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 ACPCapacity: 10 rounds1911 Size: Full SizeBlack Fluoropolymer finishStrongest 1911 magazines ever made: At least 2X the service life!Feed rails provide smoothest feeding surfaceHeavy-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 and removalLong lasting function in dirty environments