"The Phase 5 Universal Mini Stock offers a minimalist, fixed-stock solution for those looking to save weight, and bulk on their AR-15 style rifle. The UMS (Universal Mini Stock) maintains a small footprint while featuring a curved bottom to serve as an excellent anchor point, allowing you to rapidly move in and out of position with your rifle. The UMS used 2 heavy-duty set screws for simple installation on receiver extensions. The UMS is compatible with mil-spec 6-position receiver extension/buffer tubes, Phase 5 HexOne, Phase 5 Hex-2, Most cylindrical buffer tubes with 1.10""-1.25"" outer diameters, and rifle-length extension tubes. The set screw is more secure on cylindrical buffer tubes if you create indexing dimples on the tube. Note: The UMS is a stock and cannot be legally attached to pistols without converting the pistol to an SBR (Short-Barrelled Rifle) first. Minimalist design Fixed stock Curved bottom for rapid manipulation 2 set screws secure the UMS in place Compatible with mil-spec 6-position receiver extension/buffer tubes, Phase 5 HexOne, Phase 5 Hex-2, Most cylindrical buffer tubes with 1.10""-1.25"" outer diameters, and rifle-length extension tubes"