Daniel Defense 1 O'Clock Offset Rail Mount, Fits Picatinny Rail, Black Finish 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.