NRS Superston Oarlocks One Color, Pair Our proprietary manganese bronze Superston alloy gives you amazing strength and outstanding rebound memory. Built tough for the toughest jobs, they are used by outfitters the world over. The 3 1/2" long shaft is precision turned to a 5/8" diameter and is drilled for a split ring fastener (included). They fit snugly in NRS Oar Mounts. The horn opening is 1 5/8" with a 2 3/8" inside diameter. Compare the measurements under the Specs tab to those of your oar shaft to ensure a good fit with these oarlocks. Material: Proprietary Manganese and Bronze-alloyConstruction