Carlisle (aka Old Town) Clamp-On Oar Locks are used to secure rowing oars to your canoe that MUST already be outfitted with Oar Lock Sockets. Best used with Carlisle aluminum Economy boat oars. Molded of stainless steel-reinforced super tough black synthetic plastic, rustproof, rattle and squeak free. Sleeved to fit either 1/2 inch or 5/8 inch sockets. Sold in pairs. Carlisle Old Town part number 01.2510.0000. (This plastic version takes the place the discontinued Metal Version Oarlocks 01.2505.3100).