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Differences Between ESAPI & SAPI Plates

SAPI and ESAPI plates are components of individual body armor that use ceramic technology to absorb the kinetic energy of bullets and protect the wearer from serious injury. These plates are utilized by military and law enforcement personnel to minimize the harm done when bullets strike a protected area of the body. According to Stanford University, ceramic plates protect against bullets fired from rifles and pistols as well as shrapnel from explosives. The National Academies Press points out that SAPI plates are an older form of body armor capable of stopping standard rifle bullets while ESAPI plates can stop armor-piercing rifle rounds. Washington State University adds that ongoing research seeks to make armor more effective at injury prevention.

Ceramic Body Armor History
- The development of individual body armor has been ongoing since the early days of human civilization. Hardened leather, interlinked metal rings and metal sheets have all been used to protect the wearer from being harmed by weapons. Guns and gunpowder technology made most body armor obsolete due to the penetrating power of bullets fired from rifles. Ceramic plates began to dominate body armor development in the 20th century as lightweight, high-strength materials were developed that could stop bullets of many sizes.
SAPI and ESAPI Plate Mechanics
- Ceramic armor is typically composed of boron, carbon and other trace elements manufactured to be as resistant to penetration as possible. Bullets do damage to human flesh because they strike a target with such high kinetic energies that they penetrate into the body and damage organs and delicate tissues. SAPI plates and their successors, ESAPI plates, are designed to absorb as much as the kinetic energy of a bullet as possible and prevent it from penetrating the body. The energy of the impact is spread out over a wide area so that significant bruising may result, but not death due to organ destruction.
SAPI Plates: Early Ceramic Armor
- The original SAPI plates deployed by the United States military were composed of a boron carbide material and shaped to cover the majority of the upper torso of the average soldier. In testing they were rated to be capable of withstanding three strikes from 7.62mm rifle bullets, which are some of the most commonly used military bullets. Their widespread deployment has been credited with saving the lives of numerous soldiers who suffered only bruises or broken ribs rather than lethal injuries when hit by bullets.
ESAPI Plates
- ESAPI plates were developed in response to the growing use of armor piercing bullets in military rifles. These could penetrate standard SAPI plates and kill the individual wearing them. ESAPI plates had to be heavier than SAPI plates but provided an added level of protection against kinetic energy threats. In addition, ESAPI plates were developed that could protect the side of the torso and the lower torso against bullet strikes that would have penetrated personnel using only the older SAPI plates.

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