These Brass Wool snap caps feature a springloaded primer plunger that cushions and protects your firing pin during dryfiring practice, plus a wool chamber mop mounted on a metal base that can be treated with your favorite gun oil to help prevent rust in the chamber during storage; note that leaving guns cocked for long periods is hard on springs and can be dangerous, so using these snap caps helps preserve both your firearms mechanical health and safetysold 2 per pack.