Keeps your oar blade in the right position for full-power strokes. The spline of the oar right fits between the horns of an open oarlock to "lock" your oar blade in position for the most effective stroke. You can still feather the oar blade by simply tugging the oar in so the spline of the oar right clears the oarlock horns. For Carlisle and Cataract oars, use the molded oar sleeve with the oar right for proper fit. The oar right clamps securely to the Molded Oar Sleeve with two beefy stainless steel bolts Molded glass fill nylon construction will give you years of troublefree service Large: Adjusts from 2" to 2-1/4" (Carlisle & Cataraft Oars with Oar Sleeve) Small: Adjusts from 1-3/8" to 15/8" (Bluewater Oars and Economy Oars using XS Oar Sleeve) Note: Instructions that come with the oar rights say to put a screw (which is provided) through the tip of the spline into the oar shaft. This is only applicable if you're using it on a wooden oar. DO NOT do this on Carlisle or Cataract oars, as it can damage the shafts.