The AAIS BOTTOM rail, Part number BT20B is the same rail found in the BT20 but consists of the bottom 1913 rail ONLY that can be attached to the AAIS BT19 on the bottom at the 6 o'clock position. This allows mounting of the BT10 or BT10-LW17 to the AAIS BT19. This rail is 1.60 long, made from 6061T6 Aluminum with a type III hard coat anodize and are proudly made in the USA they are Black and cost $24.95.
