Superston OarLockOur best selling oarlock, the NRS Superston Oar Lock is madeproprietary manganese bronze Superston alloy gives you amazing strength and outstanding rebound memory. The 5 8" diameter, 3 1 2" long shaft is precision turned and drilled for a split ring. The horn opening is 1 5 8" with a 2 3 8" inside diameter. Oarlocks include Split Ring keepers. Don't forget to order a spare. The 3 1 2" long shaft is precision turned to a 5 8" diameter and is drilled