Many of today's pistol-caliber carbine fans are taking advantage of 9mm, but there's a subset of PCC fans that want a harder-hitting pistol caliber for their carbine. Enter the .45 ACP AR-15 M&P Conversion Adapter from Stern Defense. Designed for use with M&P pistol magazines that accept .45 ACP rounds, the Stern Defense AR-15 Conversion Adapter works with any mil-spec AR-15 lower. Installation takes mere seconds, and the adapter even has a last-round bolt hold-open feature! Each Stern Defense Mag-AD Conversion Adapter is machined from 6061-T6 aluminum and features a 4140 NiB-coated feedramp. The adapter features an ergonomic, easy-to-use magazine release and is compatible with all generations of Smith & Wesson M&P pistol magazines, so long as they accept the .45 ACP cartridge.