Oar Rights work to keep your oar blade in the right position while rowing 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. (Sleeves sold separately.) Molded glass fill Nylon construction will give you years of trouble-free service. Large: Adjusts from 2" to 2 1/4" (Carlisle & Cataraft Oars with Oar Sleeve) Small: Adjusts from 1 3/8" to 1 5/8" (Bluewater Oars and Economy Oars using XS Oar Sleeve).