A SAPI plate, or Small Arms Protective Insert, is a trauma plate that reinforces military body armor. It is typically composed of either boron carbide or silicon carbide ceramic and is capable of stopping high-velocity rounds. SAPI plates sit over the more flexible Kevlar layers that are designed to stop small rounds and shrapnel. The SAPI plate was first designed to work with the Interceptor Body Armor used by the US Armed Forces. Since then, army engineers have fitted the plates to the Improved Outer Tactical Vest and the Modular Tactical Vest.
The SAPI is judged by the US military on the number of hits from a 7.62x51 mm rifle it can take before splintering. At a minimum, a SAPI should be able to withstand at least three such hits. The higher-rated plate, the ESAPI, can withstand as many such hits from a .30 cal armor piercing round. However, this durability is only ensured if the plate is resting atop soft Kevlar. The side facing the Kevlar is lined with Spectra and absorbs much of the impact. Spectra is up to 40% more shatter-resistant than Kevlar.
Many MilSim enthusiasts are reluctant to train with their SAPIs because of the risk of damaging them. Moreover, damage to these plates is difficult to spot without the aid of x-ray imaging. The plates themselves are expensive and hard to replace in a pinch. However, a number of companies have begun to produce dummy SAPI plates that mimic the look and feel of the real thing at a fraction of the price. These dummies have the correct shape and weight to give your body armor an authentic look. For this reason, they’re ideal for training and simulation as their accurate weight and bulk will allow you to react accurately in the field. Foam inserts and other stand-ins break the illusion, allowing you to run and react faster than you otherwise would be able.
Many plates are colored in bright orange to provide protection—dummies will not stop live rounds—and to make them easy to locate in a bag of equipment. Additionally, these dummy plates are easy to find in sizes small through extra-large.