Feature Low Profile VIMW-11 30mm Diameter, 4 Screws per Ring, CNC Made Low Profile 25.4mm 1.0in from Base to Ring Center Middle Profile VIMW-12 30mm Diameter, 4 Screws per Ring, CNC Made Medium Profile 32mm 1.3in from Base to Ring Center High Profile VIMW-13 30mm Diameter, 4 Screws per Ring, CNC Made. High Profile 36mm 1.4in from Base to Ring Center. Specification Low Profile VIMW-11 Ring Length: 21mm / 0.8in Ring Dia.: 30mm Height: 25.4mm / 1.0in from base to ring center Weight: 100g / 3.5oz 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 Middle Profile VIMW-12 Ring Length: 21mm / 0.8in Ring Dia.: 30mm Height: 32mm / 1.3in from base to ring center Weight: 122g / 4.3oz 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 High Profile VIMW-13 Ring Length: 21mm / 0.8in Ring Dia.: 30mm Height: 36mm / 1.4in from base to ring center Weight: 135g / 4.8oz 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