Atlas Bipods 1913 RAIL OPTION FOR BT19 AND BT21 6 o'clock mounting position Black. 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 specialized factories they are Black and cost 24.95. Specifications for Atlas Bipods 1913 RAIL OPTION FOR BT19 AND BT21 6 o'clock mounting position: Manufacturer: Atlas Bipods Country of Origin: USA Package Contents: Atlas Bipods 1913 RAIL OPTION FOR BT19 AND BT21 6 o'clock mounting position Atlas Bipods BT20-B 1913 RAIL OPTION FOR BT19 AND BT21 6 o'clock mounting position Black