The M17 and M18 pistols have been selected by the US Military as the official sidearm, and the ROMEO-M17 is the only optic that is truly designed specifically for this pistol. All other optics have many disadvantages and make several compromises. The ROMEO-M17 does not. This is an American-built MIL-SPEC red dot truly worthy of the SIG SAUER name. *Please Note - The ROMEO-M17 pistol red dot sight utilizes SIG SAUER'S proprietary SIG-LOC mounting interface and only fits SIG SAUER M17/M18 military issue, and commemorative pistols with a single optics plate mounting screw. This sight will not fit any other pistols.