Salmon River Solutions SRS 10in Arca Tactical Rail Black. We designed this with lightweight pockets that make for an ultralight rail that looks great. This is 4 OAL and weighs only 1.3 oz. Max bolt spacing is 3.25. Specifications for Salmon River Solutions SRS Arca Tactical Rail: Manufacturer: Salmon River Solutions Color: Black Finish: Anodized Fabric/Material: 7075 Aluminum Gun Rail: Arca Gun Type: Rifle Features of Salmon River Solutions SRS Arca Tactical Rail Arca Package Contents: Salmon River Solutions SRS Arca Tactical Rail M-Lok Fasteners 10-32 Fasteners Salmon River Solutions 1119: SRS 10in Arca Tactical Rail Black