The Magpul PMAG 40 Gen M3 magazine is a 40-round 5.56x45mm NATO (or .223 Remington) polymer magazine for AR-15/M4 compatible weapons. This PMAG AR-15 magazine provides extra firepower over standard magazine size and functions flawlessly every time, no matter what conditions you encounter. Along with an expanded feature set and compatibility, this PMAG 40 magazine incorporates new material technology and manufacturing processes for enhanced strength, durability and reliability to exceed rigorous military performance specifications. A redesigned bolt-catch notch in the rear of the magazine provides increased bolt-catch clearance, while an over-travel stop on the spine helps ensure the magazine will not over-insert on compatible weapons.