This magazine features a rugged polymer body and magazine follower. The metal feed lips will stand up to thousands of rounds without any signs of wear or jams. The Ruger rotary magazine is superior to conventional feeding systems because each cartridge lies in its own channel in the magazine. This arrangement prevents jamming by eliminating the overlap between cartridge rims found with stack-type magazines. Keeping a few extra factory magazines around is never a bad idea; extra magazines save loading time at the range and also serve as a backup for those days when you simply cannot remember where you put your primary magazine.