Magpul Industries Magazine, PMAG 40 AR/M4 GEN M3, 223 Remington/556NATO, 40 Rounds, Fits AR Rifles, Black MAG233-BLK The next-generation PMAG 40 AR/ M4 Gen M3 is a 40-round 5.56x45 NATO (.223 Remington) polymer magazine for AR15/M4 compatible weapons. Along with expanded feature set and compatibility" the PMAG 40 AR/M4 Gen M3 incorporates new material technology and manufacturing processes for enhanced strength" durability" and reliability to exceed rigorous military performance specifications. While it is optimized for Colt-spec AR15/M4 platforms" modified internal and external geometry also permits operation with a range of additional weapons such as the HK 416/MR556A1/M27 IAR" British SA-80" FN SCAR MK 16/16S" and others.