Less time-consuming fitting because the proper lockup angle is pre-machined right into the bushing. Pre-Fit requires only minor fitting for installation onto Colt factory barrels. Gunsmith Fit requires fitting of both dimensions. Mfg: Egw SPECS: 416 stainless steel, silver or chrome-moly steel, blued. Pre-Fit (P/F) - .702" (17.8mm) O.D., .580" (14.7mm) I.D. Gunsmith Fit (G/F) - .702" O.D., .574" (14.6mm) I.D. Govt. (Govt.) or Commander (Comm.) length.