Differences Between Different Levels of Armor Plates

The National Institute of Justice (NIJ) classifies body armor by its ability to stop specified rounds at defined velocities. Under the long-standing NIJ Standard-0101.06, armor is grouped into five threat levels: Level IIA, Level II, Level IIIA, Level III, and Level IV. It is worth knowing that a higher level generally means protection against more powerful rounds, but the level alone does not account for other factors such as weight, comfort, or multi-hit capacity. For that reason, it is important to choose armor that fits your specific situation rather than simply picking the highest-rated option.

One note on terminology: NIJ has published a newer standard, NIJ Standard-0101.07, which is gradually replacing the familiar IIA/II/IIIA/III/IV nomenclature. Under 0101.07, handgun-rated armor is designated HG1 and HG2, while rifle-rated armor is designated RF1, RF2, and RF3. Much of the market still refers to the 0101.06 levels, so both systems are described here.

NIJ Level IIA

Level IIA armor is usually soft body armor, made from layers of high-strength woven fibers. Common fibers include aramids such as Kevlar and Twaron, or polyethylene fibers such as Spectra and Dyneema. Level IIA is tested to stop a 9mm FMJ round at roughly 1,225 ft/s and a .40 S&W FMJ round at roughly 1,155 ft/s. Most often found in soft body armor vests, Level IIA is typically the lightest, most flexible, most comfortable, and easiest to conceal.

NIJ Level II

A step up from Level IIA, Level II is also most commonly soft body armor. It is designed to stop 9mm FMJ traveling at roughly 1,305 ft/s and .357 Magnum JSP (Jacketed Soft Point) at roughly 1,430 ft/s. Like IIA, Level II armor is generally lightweight, wearable, and easy to conceal, but it offers considerably more protection against blunt-force injury (the trauma caused by the kinetic energy of a round striking the vest or plate). Because of this, many concealable vests are either Level II or Level IIIA, with Level IIA falling largely out of use.

NIJ Level IIIA

Level IIIA is designed to stop .357 SIG FMJ FN (Flat Nose) bullets traveling at roughly 1,470 ft/s and .44 Magnum SJHP (Semi-Jacketed Hollow Point) rounds at roughly 1,430 ft/s. Like IIA and Level II, Level IIIA is most commonly soft armor, though hard armor plates and ballistic shields are sometimes rated to Level IIIA as well.

NIJ Level III

At Level III, we move from soft body armor into the world of ballistic plates. These plates are also called rifle plates or hard armor plates. Level III rifle plates are tested to stop six spaced hits of 7.62x51mm NATO FMJ (U.S. military designation M80) at roughly 2,780 ft/s, which is very similar to the common .308 Winchester round. Some manufacturers also offer hard armor rifle plates rated Level III+. Although the NIJ does not formally use a III+ rating, the “+” generally signifies that a plate stops the same rounds at higher velocities, or adds protection against additional threats such as M855 and M193. Level III and III+ plates are available at a range of price points depending on plate weight and material. The least expensive options are typically steel plates, which can weigh 8–10 pounds depending on plate size, while more costly options made from polyethylene or ceramic can weigh as little as 3 pounds.

NIJ Level IV

Level IV plates are the highest-rated hard armor plates under the NIJ 0101.06 standard. They are designed to stop a single hit from an armor-piercing rifle round. Specifically, Level IV plates are tested to defeat the .30-06 M2 armor-piercing (AP) round traveling at roughly 2,880 ft/s. Keep in mind that because Level IV plates are tested against a single AP shot, while a Level III plate is tested against six shots, a Level IV plate is not automatically “better” than a Level III plate for every situation. Alongside NIJ certification, there are other standards of bullet resistance, such as the U.S. military’s SAPI (Small Arms Protective Insert) specification, which covers plates made to military requirements. That specification first appeared with the Interceptor Body Armor (IBA) and later with the Improved Outer Tactical Vest (IOTV) and Modular Tactical Vest (MTV). Since 2005, the military has moved to the ESAPI (Enhanced SAPI) program. There are also special-threat plates, designed to stop common threats while reducing cost and weight; typical examples are plates focused on AK-47 and AR-15 ammunition.

Special Threat Plates

Not every threat maps neatly onto the NIJ levels. A special threat plate is built around a specific round rather than the standardized NIJ test threats. The NIJ defines a Level III plate as one that stops 7.62×51 M80 ball and a Level IV plate as one that stops .30-06 M2 AP, but what if full-power rounds like M80 ball are not your primary concern?

Over the past couple of decades, many militaries have moved toward intermediate calibers, as have many civilian shooters and law enforcement agencies. That shift is reflected in the threats defenders actually face; many offenders and active shooters have used handguns or intermediate-caliber rifles. Complicating matters, some Level III plates cannot stop M855 ball because of its mild-steel penetrating core, since they were not built with that threat in mind.

This is why companies like HESCO offer special threat plates built around a distinct threat rather than the NIJ levels. HESCO’s L210 was a good illustration of this concept: by dropping M80 ball protection, it focused on stopping intermediate and AK-family light armor-penetrating rounds. The L210 has since been discontinued and replaced by the current HESCO L211. The L211 is a single-curve 10×12 shooter-cut special threat plate that covers the full special-rifle-threat spectrum, including 5.56 (M193, M855/SS109, M855A1), the AK-47 7.62×39 family (M67, M43, and armor-piercing incendiary), and 7.62x54R LPS. If you are shopping for light, low-visibility special threat protection today, the L211 is the plate to look at.