The new and improved Back-Up/Flip-Up A2 (AR15 BUIS) Iron Sight for Picatinny Rails. M1913 Flattop AR15 Rear Sight
A2 Back Up Iron Sight (AR15 BUIS). Improvements to the back up iron sight includes a more tactile and ergonomic windage knob, a counter sunk crossbolt, and more streamlined body.
