Premium-grade, machined stainless steel bushings ensure a close slide-to-barrel fit for the tight lockup that helps produce consistent accuracy. Heat treated and hardened to stay in spec through thousands of firing cycles. Pre-Fit requires little or no fitting on most 1911 Autos. Quick and easy way to obtain optimum accuracy and proper lock-up. Fits Nowlin, Wilson, and other .581" O.D. barrels. Oversized requires turning of O.D. and reaming of I.D. to achieve a true, match-grade fit for maximum accuracy and secure lock-up. Gunsmith fitting required.