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 Handguns At Least 2X the Service Life! Heavy-Duty Corrosion Resistant Stainless Steel Body Laser Welded Tube Numbered Witness Holes for Visual Round Count Patented RPM Follower is Alloy Frame Safe 19 Coils of High Tensile Rocket Wire Spring Removable Base Pad for Easy Cleaning Smooth Finish for Easy Insertion / Removal Long-Lasting Function in Dirty Environments