The Pro-Shot Snap Cap will allow you to store your shotgun with the cocking spring tension let off. This can add to the functional life of the shotgun and keep it in optimum working order. The Pro-Shot Snap Cap is made with a brass head with spring loaded firing pin stops for the ease of tension that is released when the trigger is pulled. Pro-Shot Snap Caps have wool mops with natural lanolin that fit into the chamber area for chamber rust protection. Oils such as Pro-Shot Zero Friction may be added to the Pro-Shot Snap Cap wool mop for extra rust protection. The mops on these caps are replaceable. *These Snap Caps are for side by side and over under shotguns only*