OPF-M17, ACRO is precision machined from 4140 steel, and QPQ coated. Aimpoint ACRO P1/P2 requires the plates to adhere to Aimpoint ACRO TDP with tight tolerances, OPF-M17, ACRO has proven to be the best choice among professional users. OPF-M17, ACRO is compatible with MIL issued M17/M18. It is a drop in adapter for superb Aimpoint ACRO sights. It is identical to the Tangodown SSM-03. OPF-M17-ACRO is shipped with two M4 0.7mm x 6mm (torque value: 20 to 25 inA lb), a T20 key, and a packet of VC-3. Proudly designed and made in the USA. Mfg: Forward Controls Design