Stab Proof Vest Protection Levels: NIJ, CAST KR1/SP1 & VPAM Compared

Introduction

If you have spent any time shopping for a stab-proof vest, you have seen the alphabet soup: NIJ 0115.00 Level 1. CAST KR1+SP1. VPAM K2/D2. EN388:2016 4X43F. GA68-2008. Each of these is a certification standard, a set of tests a vest must pass before a manufacturer can claim it protects against a specific threat at a specific energy level.

This page explains what each standard actually tests, what the numbers mean in physical terms you can feel, and how to verify that a vest is genuinely certified rather than just claiming to be. We cover the five main standards used worldwide (USA, UK, EU, China, and the EN388 industrial benchmark), compare them side by side, and provide a 5-minute checklist for spotting fake certification claims.

For the full engineering explanation of how stab armour works at the material level (fibre cut resistance, frictional dissipation, mechanical interlock, and the three stages of penetration), read our companion article: How Stab Proof Vests Stop a Knife: The Physics, Materials and Design Explained Simply.

What are Stab Proof Standards?

Stab-proof standards are testing protocols that define how protective body armour is evaluated for resistance to edged blades and spikes. They specify the test equipment (blade geometry, backing material, drop tower), the energy levels, the number of strikes, the impact angles, and the maximum allowable penetration depth. A vest that passes testing against a specific standard at a specific level can claim certification to that standard.

Without these standards, every manufacturer would test differently, and there would be no way to compare one vest against another. The standards exist so that when you buy a vest rated to NIJ Level 1, you know it has been independently verified to stop a specific blade at 24 joules with less than 7 millimetres of penetration.

Key organisations Setting Standards

Five main bodies publish the standards used to certify stab-resistant body armour:

1. National Institute of Justice (NIJ), USA. The NIJ sets standards widely recognised for protective gear, including stab-proof vests. Their NIJ 0115.00 standard uses rigorous testing with clear protection levels.
2. Centre for Applied Science and Technology (CAST) and Home Office, UK. CAST provides standards for UK law enforcement and personal protection equipment. The CAST 2017 standard replaced the older HOSDB 2007 standard.
3. Vereinigung der Prüfstellen für Angriffshemmende Materialien und Konstruktionen (VPAM), Germany. VPAM standards are used across Europe for comprehensive testing and high protection levels. VPAM KDIW 2004 covers stab and impact resistance.
4. Ministry of Public Security, China. The GA68-2008 standard is China's national certification for stab-proof body armour, used for police and security operations.
5. European Committee for Standardization (CEN). EN388:2016 is the European standard for protective gloves against mechanical risks. While not a stab-armour standard, its puncture and cut resistance tests are widely referenced for the fabric layers inside stab vests.

We walk through each standard below, highlighting the key elements without overwhelming detail.

NIJ Standard-0115.00 (USA)

The NIJ Standard-0115.00 specifies the performance requirements and testing methods for stab-resistant body armour used by US law enforcement. The armour is categorised into two protection classes, "Edged Blade" and "Spike", with three protection levels (1, 2, and 3) for each class.

For any given protection level, the armour must withstand impacts at two distinct energy levels:

• E1 Energy Level: The normal strike energy the armour is expected to handle in the field.
• E2 Energy Level: An overtest condition where the strike energy is increased by 50% to ensure a safety margin.

The allowable penetration depths are:

• E1 Energy Level: Maximum allowable penetration is 7 mm (0.28 inches). This limit is based on research indicating that internal injuries to organs are extremely unlikely at this depth.
• E2 Energy Level: Maximum allowable penetration is 20 mm (0.79 inches). The higher limit under overtest conditions still keeps the blade away from vital organs.

NIJ Protection Levels and Corresponding Strike Energies

Key takeaway: The NIJ standard prioritises practical wearability over absolute impenetrability. Even if a blade pierces slightly (≤7mm), the goal is to prevent life-threatening injury. A vest that is rigid enough to allow zero penetration would be too stiff to wear for a full shift. The standard balances protection with the reality that armour must be worn to work.

VPAM Standard KDIW 2004 (Germany/EU)

The VPAM Standard KDIW 2004, developed by the Association of test laboratories for bullet-resistant materials and constructions, outlines the requirements, classifications, and test procedures for stab and impact-resistant protective equipment, including body armour, protective helmets, and shields.

VPAM Protection Classes

The standard categorises protective equipment into classes based on resistance to different threat tools:

• Knife (blade): K1 to K4
• Nail (spike): D1 to D4
• Injection cannula: I1
• Block (impact): W1 to W5

Testing Procedures

• Stab Resistance: Testing with knives, spikes, and injection cannulas at specified energy levels and conditions.
• Impact Resistance: Testing with a block to simulate the impact of thrown or striking objects with edges.

The standard specifies the dimensions, materials, and preparation of test tools. Tests are conducted using a drop test apparatus to ensure the tools strike test specimens at the correct energy levels and angles.

VPAM Penetration Limits

• Knife (K1 to K4): less than 20 mm in general areas, 25 mm at seams and overlaps.
• Nail (D1 to D4): less than 20 mm in general areas, 25 mm at seams and overlaps.
• Injection cannula (I1): must not puncture the test specimen.

The standard requires detailed documentation of the testing process and results, including a test report and certificate if the equipment passes.

CAST 2017 Standard: Protection Levels and Penetration Depths (UK)

The CAST 2017 standard for stab-resistant body armour defines two primary knife protection levels (KR1 and KR2), which can be upgraded to include spike protection (SP1 and SP2). For each knife protection level, there are two stab energies assessed: E1 and E2. Spike protection is only assessed at E1.

Knife Protection Levels

Knife and Spike Protection Levels

These penetration limits are absolute, with no rounding permitted. At energy level E1, one penetration in a test series is permitted up to the Single Penetration Limit (SPL); at energy level E2, one penetration is permitted up to the E2 SPL. All other penetrations must be within the standard limits.

Key difference from NIJ: UK CAST incorporates multi-angle strikes and accounts for unpredictable attack patterns, reflecting the diversity of threats in urban policing. CAST spike protection (SP1/SP2) requires zero penetration, whereas NIJ allows up to 7 mm. Both standards allow a certain level of knife penetration so that body armour can be designed to prevent life-threatening penetrations while allowing a degree of comfort and wearability.

GA68-2008: China's Stab Protection Standard

China's GA68-2008 standard, released by the Ministry of Public Security for police operations, has one defining characteristic that sets it apart from Western standards: it requires zero blade penetration for certification. Where NIJ 0115.00 allows up to 7 mm of penetration at the E1 energy level, and CAST 2017 allows up to 8 mm, GA68 treats any breach of the inner layer as a failure.

The standard tests at 24 joules of strike energy using a standardised prison-style dagger. Vests must pass at both 0° (perpendicular) and 45° impact angles. Every strike must leave inner layers intact: no torn threads, no punctures, no penetration of any depth.

GA68 also imposes environmental conditioning requirements beyond most other standards. Armour must pass testing after exposure to temperatures from -20°C to +55°C, and after sweat corrosion and UV exposure conditioning. Seams and joins face targeted 45° strikes, testing potential weak points that most standards do not separately evaluate.

This zero-penetration requirement has practical implications. At an identical 24J impact energy, NIJ Level 1 permits up to 7 mm of blade penetration, which is enough to break skin and carry infection risk from contaminated blades. GA68 treats that same breach as a failure. For contexts where even superficial wounds carry serious consequences (bloodborne pathogen exposure in correctional facilities, for example), the zero-penetration standard provides a higher margin of safety. The trade-off is that GA68-compliant armour tends to be heavier and less flexible than armour designed to NIJ's penetration-allowing thresholds.

ArmorLite's FlexGuard series has been independently tested to GA68 by CNAS-accredited laboratories, achieving zero penetration at 24J. The same panels have been tested beyond NIJ Level 3 E1 requirements (43J), stopping blades at energies up to 55J in CNAS laboratory tests, and maintaining performance after 72-hour sweat immersion and -40°C thermal cycling.

EN388:2016: The Industrial Cut and Puncture Benchmark

EN388:2016 is not a stab-armour standard. It is the European standard for protective gloves against mechanical risks. But it matters for stab vests because the textile layers inside body armour are often tested to EN388 for cut and puncture resistance.

The standard measures four properties, each rated on a numerical scale. The resulting four-digit rating (plus optional fifth and sixth digits for impact and blade cut) appears on certified protective equipment:

• Digit 1, Abrasion resistance (1-4): Cycles to failure under sandpaper.
• Digit 2, Blade cut resistance, Coup test (1-5): A circular blade under fixed pressure cycles back and forth until cut-through. Counts cycles relative to a standard cotton reference fabric.
• Digit 3, Tear resistance (1-4): Force required to tear a pre-cut sample.
• Digit 4, Puncture resistance (1-4): Force required to push a 4.5 mm diameter probe with a 1.0 mm tip radius through the material at 100 mm/min. Level 4 requires ≥150 N.
• Digit 5 (optional), Blade cut resistance, TDM-100 test (A-F): A straight razor blade drawn across the material under increasing force until cut-through. This is the test most relevant to slash protection for stab vests.
• Digit 6 (optional), Impact protection (P/F): Pass or fail for impact attenuation.

Critical distinction: EN388 puncture (Digit 4) is not a stab test. The test uses a blunt 4.5 mm probe pushed at 100 mm/min (quasi-static). A knife strike delivers roughly 24 J at 5 metres per second. The energy delivery rate differs by a factor of roughly 20,000×. A material passing EN388 Level 4 puncture (≥150 N) can still fail against 24 J of dynamic knife impact. EN388 puncture is relevant to industrial hazards (nails, metal splinters), not to weapon threats.

That said, EN388 cut resistance (Digits 2 and 5) is directly relevant. The TDM-100 slash test (Digit 5) uses a real razor blade drawn across the material, and the A-F scale provides a meaningful measure of how well the fabric resists being cut open by a slashing motion. For comprehensive protection, a vest needs both a weapon-level stab certification (NIJ/CAST/VPAM) for thrusts and high EN388 cut ratings for slashes.

ArmorLite's SoftGuard fabric achieves EN388:2016 Level 4 puncture resistance at 450N (3× the 150N Level 4 threshold) and ANSI/ISEA 105 A8 cut resistance.

What do These Impact Energy Levels Mean?

Certification joules are abstract. Here is what they mean in physical terms you can feel:

Physics note: these analogies use E = mgh (potential energy = mass × gravity × height). A 24 J impact equals roughly a 5 kg mass dropped from 0.5 metres onto a knife tip: the weight of a 5-litre water bottle dropped from table height, concentrated onto an area smaller than a pinhead.

How to Verify a Stab Vest Is Actually Certified: A 5-Minute Checklist

A label that says "NIJ certified" is not enough. Anyone can print those words on a tag. Every month, people buy stab vests online believing they are protected, only to discover the vest was never independently tested to any recognised standard. An untested vest is not just a waste of money. It creates a false sense of security that can put the wearer in more danger than wearing no armour at all.

"NIJ Certified" vs "NIJ Tested": Know the Difference

The most important distinction to understand before you check anything else: "NIJ certified" and "NIJ tested" are not the same thing. Confusing the two is how most buyers end up with untested armour.

NIJ certified means the vest model has been submitted to an NIJ-approved laboratory, passed all tests, and is listed on the NIJ Compliant Product List (CPL). Certified models undergo ongoing follow-up surveillance testing through the Compliance Testing Program (CTP). The manufacturer cannot change materials, construction, or design without re-testing.

"NIJ tested" or "tested to NIJ standards" means a manufacturer sent a single sample to a laboratory of their own choosing, under conditions of their own choosing, without independent oversight. There is no follow-up. There is no CPL listing. The language is designed to sound like certification without the substance behind it.

The 5-Minute Verification Checklist

Run through these five steps before buying any stab vest. If any step fails, the vest's certification claims should be treated as unverified. An ISO 17025-accredited lab test report naming the specific standard and result provides independent verification that is equally valid as formal certification. The key is independent testing by a recognised laboratory, not just the manufacturer's own claims.

1. Check the NIJ Compliant Product List. Go to cjttec.org/cpl-stab-armor. Search for the manufacturer name and model number. If the model is not on the CPL, it is not NIJ certified: regardless of what the product listing says. This is the single most definitive check and takes 30 seconds.
2. Look at the certification label inside the vest. A legitimate NIJ-certified vest must carry a permanent internal label showing: manufacturer name, unique model identifier, NIJ 0115.00 standard designation, protection class symbol (blue square for Edged Blade / green triangle for Spike), protection level achieved, and a compliance statement. If the product listing does not include a photograph of this label, ask the seller to provide one before buying.
3. For UK vests, check the Home Office PED. CAST-certified models appear on the Police Equipment Database. If it is not there, it has not been CAST tested, regardless of what the seller claims.
4. Look for the standard number, not just the name. "NIJ certified" is meaningless on its own. "NIJ 0115.0 Level 1" with a listed lab and test date is real. Same for EN388: it must say "EN388:2016" with the full rating string (for example, 4X43F). The full standard designation including version year tells you the lab followed a specific, published test protocol rather than an internal procedure.
5. Check the price. A vest claiming NIJ or CAST certification at £30-50 is almost certainly fake. Independent lab testing costs thousands of pounds. Real certified vests start around £100-150. If the price seems too good to be true, the certification almost always is too.

The simplest test: If a vest is sold on Amazon or eBay without a linked lab report, and costs under £50, assume the certification claim is false until proven otherwise. Legitimate manufacturers make their test documentation available. If you have to chase a seller for it, that is your answer.

Every ArmorLite product includes independent lab reports and certification documentation. Browse our certified range →

Comparing Standards: A Side-by-Side Summary

Choosing the Right Standard for You

Which certification level you need depends on your risk profile:

• Security guards, door supervisors, and lone workers in medium-risk roles: NIJ Level 1 (24J) or CAST KR1 provides tested protection against the force roughly 85% of adults can deliver. This is the most common certification level for professional security use in the UK.
• High-risk security, cash-in-transit, and prison officers: NIJ Level 2 (33J) or CAST KR2 covers stronger attackers and two-handed thrusts. Consider adding spike protection (SP1/SP2 or NIJ Spike Level 1+).
• Maximum protection for worst-case scenarios: NIJ Level 3 (43J) combined with spike certification. This stops near-maximum human force, including running thrusts with combat knives.
• Everyday wear and delivery drivers: A lightweight covert vest at NIJ Level 1 with high EN388 cut ratings provides meaningful protection at a weight you will actually wear. The best certification in the world means nothing if the vest is too heavy to put on.

Two things to remember: First, certification only applies to the specific model tested. A manufacturer with one certified model does not mean all their products are certified. Check each model individually. Second, certification is a minimum standard, not a guarantee. A vest certified to NIJ Level 1 at 24J stops a specific blade at that energy under laboratory conditions. Real attacks are messier. But independent certification is the best evidence we have that a vest will perform when it counts.

Frequently Asked Questions

What are the different stab vest ratings?

There are five main standards for stab protection levels worldwide. NIJ 0115.00 (USA) has three levels: Level 1 (24J), Level 2 (33J), and Level 3 (43J). UK CAST 2017 has two knife levels: KR1 (24J) and KR2 (33J), each with optional spike protection SP1 and SP2. Germany's VPAM KDIW 2004 has knife classes K1 through K4 and spike classes D1 through D4. China's GA68-2008 has a single level at 24J but requires zero penetration to pass, which is stricter than NIJ or CAST. EN388:2016 is an industrial standard for gloves, not a stab armour standard, but its cut and puncture ratings are widely referenced for the fabric layers inside stab vests. For most civilian and security buyers, NIJ Level 1 (24J) or CAST KR1 is the appropriate protection level. It covers the force roughly 85% of adults can deliver with a knife. The table in Section 6 above shows a side-by-side comparison of every standard.

Is level 3 or level 4 body armor better?

This question usually refers to ballistic (bulletproof) armour, not stab armour, and the naming overlap causes real confusion. NIJ ballistic levels use Roman numerals: Level II, IIIA, III, and IV. NIJ stab levels use Arabic numerals: Level 1, 2, and 3. A "Level 3" ballistic vest stops rifle rounds. A "Level 3" stab vest stops a 43J knife thrust. They test against entirely different threats using entirely different methods. If you are comparing bulletproof vests, NIJ Level IV is higher than Level III and stops armour-piercing rifle rounds. If you are comparing stab vests, NIJ Level 3 (43J) is higher than Level 2 (33J) and Level 1 (24J). But a Level 3 stab vest will not stop a bullet, and a Level IIIA ballistic vest will not stop a knife. Always check which standard the level number refers to. For more detail, see our article on the difference between stab proof and bulletproof vests.

What is the difference between stab and ballistic protection levels?

They test completely different threats. Stab standards (NIJ 0115.00, CAST, VPAM, GA68) drop a sharpened blade or spike onto the armour from a known height and measure penetration depth in millimetres. Ballistic standards (NIJ 0101.06/0101.07) fire bullets of specific calibre and velocity at the armour and check whether any round penetrates. A vest can pass every ballistic test and fail every stab test, because the mechanisms are different: bullets are stopped by stretching fibres across a large area, while knives are stopped by cutting individual fibres. This is why stab vests and bulletproof vests are built from different materials in different architectures, and why a vest claiming dual certification must be tested against both standards separately. The energy comparison is not intuitive either: a 9mm handgun round carries roughly 500 joules, more than ten times the 43J of a NIJ Level 3 knife thrust. But the knife concentrates its 43J onto a tip area thousands of times smaller than the bullet's frontal area, so the local pressure can actually be higher.

Why are there so many £30-50 "NIJ certified" vests on Amazon?

Because the phrase "NIJ certified" is not regulated at the point of sale. Anyone can print those words on a product listing. The real check is whether the model appears on the NIJ Compliant Product List at cjttec.org. Most £30-50 vests on Amazon are not on that list. They typically use steel plates (heavy, not independently tested) or thin foam layers (no real protection). Independent lab testing costs thousands of pounds per model. A vest sold for £30 with free delivery cannot have been independently tested at that price point. The budget Amazon buyer is not wrong to want protection. But the upgrade path is predictable: buy a £50 vest, discover it is too heavy or the certification does not check out, then search for a properly certified lightweight vest. If you can skip step one, you save money and get protected sooner.

Will a certified stab vest make me look like a police officer or security guard?

Only if you choose an overt vest worn on top of your clothing. Covert vests certified to NIJ 0115.0 Level 1 or CAST KR1 are designed to be worn under a shirt, hoodie, or jacket. They are roughly the thickness of a fleece and are not visible from the outside. The fear of looking like a target or being mistaken for law enforcement is a real concern raised repeatedly by civilian buyers. The answer is to choose a covert vest and wear it under your normal clothes. Nobody will know you have it on, which is the point.

How do I wash and maintain a certified stab vest?

The protective panel inside a certified vest cannot be machine washed or dry cleaned. Washing damages the fibre structure that provides the certified protection. The outer carrier vest that holds the panel can usually be removed and machine washed at 30 °C. Between washes, wipe the panel with a damp cloth and let it air dry completely before reassembling. Do not use bleach, fabric softener, or a tumble dryer on any part of a stab vest. If the panel gets saturated (heavy rain, sweat over months of daily wear), replace it. Most manufacturers recommend panel replacement every 5 years under normal use, sooner with heavy daily wear. ArmorLite's SoftGuard fabric is machine washable in its entirety because the protective knit is the garment itself, not a removable insert. Check your specific vest's care label. Following it is not optional if you want the certification to remain valid.

Additional Resources

• How Stab Proof Vests Stop a Knife: The Physics Explained: The five mechanisms that stop a blade, in plain English.
• Are Stab Proof Vests Legal in the UK?: UK body armour laws explained.
• Stab Proof vs Bulletproof: What's the Difference?: Why ballistic vests fail against knives.
• UK Knife Crime Statistics 2026: The data behind why people choose to wear protection.

Related reading: the latest UK knife crime statistics, updated for 2026.

Browse Certified Stab-Proof Vests →

Every vest includes independent lab certification. Free UK delivery. 30-day returns.