FatBoy Tripods Arca Rail KeyMod OD Black. The M-Lok Arca Rail Mount is made with the finest materials and is designed to be mounted to 1.5in/38mm Arca-Swiss tripod clamps. Try it out for yourself and experience the convenience and versatility of the FatBoy M-Lok Arca Rail Mount Specifications for FatBoy Tripods Arca Rail: Manufacturer: FatBoy Tripods Color: OD Black Fabric/Material: Aluminum Gun Type: Rifle Length: 5 in Width: 1.5 in Weight: 0.67 lb Package Contents: FatBoy Tripods Arca Rail FatBoy Tripods FBTKMOD5: Arca Rail KeyMod OD Black