Atlas Bipods M-LOK Rail Black. It has 3 usable slots for attaching any of our 1913 Picatinny rail mounted Atlas Bipods Accu-Shot Monopods or Folding Foregrip. It requires standard M-LOK sized slots for mounting. Specifications for Atlas Bipods BT73 M-LOK Rail: Manufacturer: Atlas Bipods Color: Black Length: 1.575 in Finish: Type III Hard Coat Anodized Fabric/Material: 6061-T6 Aluminum Country of Origin: USA Package Contents: Atlas Bipods Bipods BT73 M-LOK Rail Two 10-24 x 3/8 Fasteners Two M-LOK Nuts Atlas Bipods BT73: Bipods BT73 M-LOK Rail Black