This is 12 Gauge Armor Piercing Ammo. This ammo contains a specially made high velocity slug that has a steel core swaged into the middle of the slug. The base of the slug is solid lead, formed into a flat surface to help punch the steel core through the target. This ammo will typically defeat steel targets up to 1/4" thick. This is a 2 3/4" round loaded to a max charge. It is safe to shoot in all 12 gauge shotguns.