This item is a low picatinny rail mount for the Trijicon RMR (Ruggedized Miniature Reflex).
Trijicon Low Picatinny Rail Mount for RMR, RM33 is compatible with Mil-Std 1913 Picatinny rail mounting system. This Red Dot Sight Accessory by Trijicon is designed for Trijicon RMR Red Dot sights.