Convert your standard mil spec AR 15, M4, M16 lower assembly to use 9mm and .40 S&W M&P and P320/P250 Magazines! The Mag-AD series adapters install in seconds. Boasting a last round hold open feature making them a breakthrough product and a must-have for law enforcement and civilian gun enthusiasts alike. The Stern Mag-AD series adapters are made of aircraft grade aluminum, lightweight with ergonomic design. Note: These adapters require the use of a 9mm or 40S&W barrel, "depending on chosen caliber" and a Glock cut bolt. Features: Made in the U.S.A. Constructed from 6061 T6 aircraft grade aluminum. 4140 NiB coated feed ramp. Hard coat anodized type 3. Sturdy Construction. Ergonomic mag release. Works with all generations of M&P magazines. Works with P320 and P250 magazines Works with any mil spec AR-15 lower receiver. All gun components besides the Bolt and Barrel remain stock