This is a replacement 10/22 bolt stop pin that's made out of a special shock absorbing material. It replaces the big sideways pin at the rear of the bolt on your Ruger 10/22 receiver. Some call it a "Recoil Buffer" and others call it a "Bolt Buffer"... The latter is more accurate. When you fire, your 10/22 bolt cycles backward and may contact the original steel bolt stop pin with enough impact to eventually cause some damage. By replacing the original steel pin with this shock absorbing pin, you will protect your 10/22 from this wear and tear. Click Here to see all of our many other Ruger 10/22 Accessories!