Vector SBR Gen II .45 ACP 5.5 Inch Threaded Barrel Defiance M4 Stock with Adaptor Black 13 Round All NFA Rules Apply Kriss Usa Vector SBR Gen II Super V Recoil Mitigation System. Toolless caliber interchangeability. Glock magazine compatible. M4 stock adaptor with fixed Defiance M4 stock. Smooth pivoting trigger with audible and tactile reset. Ambidextrous short throw safety lever. 4-pin toolless disassembly. Low-profile folding sights, full length picatinny top rail, lower picatinny accessory rail and a Glock magazine. All NFA Rules Apply.