Feature 25.4mm 1in Diameter, 4 Screws per Ring, CNC Made Medium Profile 25.4mm 1.0in from Base to Ring Center Specification Ring Length: 21mm (0.8in) Ring Dia.: 25.4mmn 1in Height: 25.4mm 1.0in (from base to ring center) Weight: 104g (3.7oz) Material: 6063-T6 aluminum alloy Finish: Black matte Easy and quick installation Fit on 21mm picatinny and weaver rail Designed for real firearms With connection to SCACD-22 Screw-in Anti Cantilever Device Mount (ACD mount not included) 1 pc T10 torx wrench