CMMG MK4/AR-15 Gen 2 Series Replacement Magazine 5.7x28mm 32 Round Black 1 Pack Polymer 32RD. 7 AR Conversion Magazines feature a number of improvements. From the stylized texture grip and 5.7x28mm engraving on the sides to the upgraded feed lips these magazines are built to exceed your expectations. 5.7 AR Conversion Mags are available in 32 or 10 round capacity and are designed to work with CMMG 5.7x28 Radial Delayed Blowback Uppers and Mk4/Mil-Spec AR15 lower receivers. Specifications for CMMG MK4/AR-15 Gen 2 Series 5.7x28mm 32 Round Replacement Magazine: Manufacturer: CMMG Color: Black Fabric/Material: Polymer Magazine Capacity: 32 Round Caliber: 5.7x28mm Gun Make: AR Platform Package Contents: CMMG MK4/AR-15 Gen 2 Series 5.7x28mm 32 Round Replacement Magazine CMMG 54AFCC8-32RD: MK4/AR-15 Gen 2 Series Replacement Magazine 5.7x28mm 32 Round Black 1 Pack Polymer