Carlson's Choke Tubes, 12 and 20 Gauge Wool Snap Caps have spring-loaded primer plunger to prevent firing pin damage during dry-firing exercises. Treat the wool chamber mop on this Shooting Accessory manufactured by Carlson's Choke Tubes with you favorite gun oil to prevent rusty chambers during storage. The 12 & 20 Gauge Wool Snap Caps by Carlson's are designed to help keep your firearm in perfect condition. We are excited to provide our customers with the full line of Carlson's Shotgun Choke Accessories available in our online store.