Salmon River Solutions SRS 4in Arca Rail Black. Made from 7075 aluminum we were able to come up with an extremely light rail while utilizing full-length slots for flexible mounting options. 11'' has a flare at the end for bottom metal. Specifications for Salmon River Solutions SRS Arca Rail: Manufacturer: Salmon River Solutions Color: Black Finish: Anodized Fabric/Material: 7075 Aluminum Gun Rail: Arca Gun Type: Rifle Length: 4 in Features of Salmon River Solutions SRS Arca Rail Arca Package Contents: Salmon River Solutions SRS Arca Rail M-Lok Fasteners 10-32 Fasteners Salmon River Solutions 1114: SRS 4in Arca Rail Black