Boron carbide (chemical formula approximately B4C) is an extremely hard boron–carbon ceramic, a covalent material used in tank armor, bulletproof vests, engine sabotage powders, as well as numerous industrial applications. With a Vickers hardness of >30 GPa, it is one of the hardest known materials, behind cubic boron nitride and diamond.

A bulletproof vest, also known as a ballistic vest or a bullet-resistant vest, is an item of body armour that helps absorb the impact and reduce or stop penetration to the torso by firearm-fired projectiles and fragmentation from explosions. The vest may come in a soft form, as worn by many police officers, prison officers, security guards, and some private citizens, used to protect against stabbing attacks or light projectiles, or hard form, using metallic or para-aramid components. Soldiers and police tactical units wear hard armour, either in conjunction with soft armour or alone, to protect against rifle ammunition or fragmentation.