Patented KRISS Super V Recoil Mitigation System For Glock(TM) Magazine Compatible Smooth Trigger with Audible and Tactile Reset Toolless Caliber Interchangeability Ambidextrous Short Throw Safety Lever Full Length MIL-STD 1913 Picatinny Top Rail MIL-STD 1913 Picatinny Bottom Rail Low Profile Folding Sights KRISS M4 Stock Adaptor with DEFIANCEA(R) M4 Stock 4-pin Toolless Disassembly OPERATING: SYSTEM: Closed Bolt Delayed Blowback ACTION TYPE: Semi-Automatic TRIGGER TYPE: Pivoting Single Stage TRIGGER WEIGHT: 5.5 lbs SAFETY: Ambidextrous MAGAZINE RELEASE: Button Left Side MAGAZINE COMPATABILITY: For Glock(TM) G21 Magazine