Small-arms protective insert

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The Small Arms Protective Insert (SAPI) is a plate used in the Interceptor body armor, a new-generation bullet-resistant vest. The kevlar Interceptor vest itself is designed to stop projectiles up to and including 9mm submachine rounds, in addition to fragmentation. To protect against rifle fire in critical areas, supplemental plates are needed.

It is made of boron carbide ceramic. It is able to stop up to three rifle bullets of caliber smaller or equal to 7.62 mm and muzzle velocity smaller or equal to 2,750 feet per second (838 m/s). The ceramic plate is backed with Spectra shield, a material up to 40% stronger than Kevlar.

The individual plate weighs about 4 pounds, and costs about USD 350 to produce. There is one for the front of the body, one for the back.

The mechanism of effect lies in absorbing and dissipating the projectile's kinetic energy in local shattering of the ceramic plate and blunting the bullet material on the hard ceramic. The Spectra backing then spreads the energy of the impact to larger area and stops the fragments, preventing an injury of the wearer.

The same principle is used for the ceramic tiles used for the armored cockpits of some military airplanes, and the spall liners used in modern armoured personnel carriers.