This is a Daniel Defense Mount, model 03-029-13017.
Daniel Defense's One O'clock Offset Rail (Rock & Lock) is optimized for mounting miniature red dot optics in the 1 O'clock (right-hand) or 11 O'clock (left-hand) positions for quick" non-magnified" transitions when employing magnified primary optics on AR-type rifles with MIL-STD-1913 rails. The geometry allows for zero cheek-weld shift during the transition. This facilitates very fast transitions from magnified to non-magnified optics" and back. The 1 O'clock Offset Rail can also be used to mount a variety of lights or other accessories that mount to a MIL-STD-1913 rail. By flipping the part upside-down" one can mount a light in a good position for use with a vertical foregrip.
Features:
Patented Rock & Lock one piece mounting system
Optimized for Miniature Red Dot Optics
Zero Change in cheek weld for transitions
Fast Transitions
