THE PRO-SHOT 12 GAUGE SEMI-AUTO SNAP CAPS ENSURE NO UNDUE STRESS OR IMPACT COMES TO YOUR GUN WHEN DRY-FIRING. Be careful. Dry-firing can cause stress and impact damage to your firing pin. In fact, your gun could even experience a barrel breech. The Pro-Shot 12 Gauge Semi-Auto Snap Caps ensure this doesn't occur. This two pack works excellently with semi-auto, over/under, and side by side 12 gauge shotguns.