The RPM design is the result of a relentless pursuit of excellence, maximizing reliability and durability under all conditions. The dual wall feed rails have revolutionized 1911 magazines. Caliber: .45 ACP Capacity: 10 rounds 1911 Size: Full Size Black Fluoropolymer finish Strongest 1911 magazines ever made: At least 2X the service life! Feed rails provide smoothest feeding surface 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 and removal Long lasting function in dirty environments