Trauma plate A trauma plate , also known as a trauma pack , is a plate that is an add - on component / insert to a ballistic vest . Its primary purpose is to absorb and disrupt the kinetic energy of a bullet impact and reduce the blunt trauma transferred to the wearer of the vest . Trauma plates typically enhance the ballistic value ( how " bulletproof " it is ) of the part of the vest that they are positioned behind . Trauma plates are most commonly found in a pocket in front of the ballistic panel of a vest and positioned in the center of the chest . Some vests feature plate pockets in the back of the vest as well as the front . Some advanced tactical and demolition vests accommodate a multitude of trauma plates . Shapes and sizes . Trauma plates can be found in a variety of sizes and shapes . The most common shapes are rectangle , rounded rectangle and irregular hexagon . In concealed vests ( vests worn under a shirt ) , the trauma plates are most commonly 5 ″ × 8 ″ , with variants including 5 ″ × 7 ″ , 5 ″ × 9 ″ , 6 ″ × 8 ″ , and 6 ″ × 9 ″ . Thickness ( depth ) varies based on material and application but rarely exceed 1 / 4 ″ . In tactical vests , worn as outerwear , the trauma plates are most commonly 10 ″ × 12 ″ with some variation depending on the vest . Thickness varies , depending on material and application , but rarely approaches 1 / 2 ″ . In specialized / military - grade vests , a considerable portion of the vest is made up of rigid , trauma - plate like inserts . Since they are an essential part of the vest , they are NOT typically considered the same as trauma plates and are typically referred to as inserts , much like the aramid ballistic inserts found in concealed , duty , and tactical vests . SAPI vests are an example of this type of vest . In most SAPI based vests / carriers , the outer vest is made out of and lined with aramid material is made to carry multiple ballistic inserts , typically made out of ceramics . These inserts are shaped to fit the carrier and have sizes that vary depending on the size and shape of the vest . Materials . Most trauma plates are made of a combination of materials . The following categories denote the primary material used in different plate packages . Ceramic . A ceramic is a non - metallic , inorganic material , like glass - but much stronger and consisting of a variety of possible materials . Ceramic plates , typically composed of boron carbide or near variants , are very popular in military application . These materials offer very high ballistic value . However , they do not do very well at dispersing blunt trauma . As a result they are often backed with materials like aramid fabrics , high density plastics , and / or metals . Metal . Most metal trauma plates are made primarily of steel or titanium . Aluminium and various alloys also exist . Metal trauma plates are typically considered the best for reducing blunt trauma , thanks to the conductive traits of the material . There are stories of bullets sliding or bouncing off of metal trauma plates and injuring the wearer ( shots deflected off the chest and hitting the head ) . As of this writing , stories of such claims are unverified and unlikely , as the trauma plate is typically positioned behind the aramid fabric / panels of the vest , and the likeliness of a bullet passing through the fabric , ricochet ing , and passing through more aramid fabric is very unlikely . However , to address this fear , many metal plates are encased in special materials designed to trap the bullet and / or its fragments . Fabric . Often called , Soft trauma plates , these are flexible plates that typically do little to reduce trauma . They are typically composed of layers of aramid fabrics , similar to , if not the same as the material found in the vest . They may also include thin sheets of metal or ultra high molecular weight polyethylene ( UHMWPE ) to add stiffness and some trauma protection . Plastic . Multi - layered sheets / plates of ultra high molecular weight polyethylene ( UHMWPE ) can provide an added ballistic enhancement equal to or even greater than metal plates with less weight . With these , there is the cost of less trauma reduction and the improbable but possible risk of fracture . The layered sheets that exist in each plate , are sometimes separated by high density foam , which provides some compression to aid in dissipating the kinetic energy of an impact . Though this is more often found in cheap polycarbonate plates that provide some trauma reduction , but no ballistic value . Nanomaterials . Proposed to be the future for both trauma plates and anti - ballistic fabrics , carbon nanotube and nanocomposite materials offer a new strength to weight ratio that exceeds current materials . For further information on these materials as applied to ballistics , please visit the section on ballistic vest nanomaterials in ballistics . Though nanotechnology processes are used to enhance modern ballistic materials , no " nanomaterials " are currently available in commercial products . Special Threat Plates . Special threat plates ( STP ) , also known as multi - threat , special purpose , rifle , and special application plates , are plates that have a notably higher ballistic rating ( NIJ standard ) than the vest . There is no standard for materials or ballistics for these plates , though most meet the NIJ Standard for armor type III . Many of these plates are made of a combination of materials , like ceramic on plastic , plastic on metal , etc . Some manufacturers use these labels more for marketing than really offering enhanced protection .