The CMC Products Railed Power Mag magazine is a dual wall feed rail magazine, so you have no more jams due to thin, warped and bent feed lips. The feed rails built into the RPM are at least twice as strong as traditional 1911 magazine feeds lips and provide a much smoother feeding surface..45 caliber fits All Full-Size (Government Model) 1911 HandgunsAt Least 2X the Service Life!Heavy-Duty Corrosion Resistant Stainless Steel BodyLaser Welded TubeNumbered Witness Holes for Visual Round CountPatented RPM Follower is Alloy Frame Safe19 Coils of High Tensile Rocket Wire SpringRemovable Base Pad for Easy CleaningSmooth Finish for Easy Insertion / RemovalLong-Lasting Function in Dirty Environments