Makes the magazine easier to load, helps it to fall clear when empty, and the weight calms down the recoil. Very nice part. Perfect for USPSA's "Limited-10" division, and for anyone required to use 10-round magazines (thinking of you, Hawaii and Canada). (Mr. Taylor uses these on his bowling-pin guns for added recoil control.) Due to U.S. State Department restrictions, we cannot ship this part internationally.