The wear rings aid in stopping speed-robbing cavitations in your worn jet pump Our SBT Delrin wear rings and liners will restore the tight clearance to your impeller A Jet Ski wear ring is a sacrificial ring that is installed into the jet pump to provide a minimal clearance for the impeller to build thrust More specifically, SBT has engineered our replacement Jet Ski wear rings for reduced friction using one hundred percent Delrin instead of fiberglass filled plasticsPolyoxymethylene or polyacetal, commonly known as Delrin, is an engineering thermoplastic used in precision parts that require high stiffness, low friction and excellent dimensional stability The Delrin wear rings have very low water absorption and are chemically resistant because they are acetal based plasticsThe SBT wear rings perform better and are more economical, which allows you to replace the wear ring every time you are doing work on the jet pump Yamaha: Please note that SBT liners will work only with SBT jet pump housings and not OEM jet pump housings.