Lee Smart Lock Breech Lock Bushings feature an easy grip splined drive surface which allows easy, accurate and fast die installation in your press. No need for lock rings on your dies with these quick-change bushings. An internal o-ring maintains perfect adjustment. Once set, you'll never lose position. They look so good and work so well, you'll want them for all your dies. For even easier installation, Lee makes a handy lock ring wrench (sold separately).