Rubber reducer allows a lower radiator hose with a molded-in spring to be used as an upper radiator hose. In continuous high RPM applications, the upper hose can collapse limiting coolant flow. Upper hoses with an internal spring support can also collapse if the spring is drawn into the radiator tank. Reducer fits inside 1-3/4" lower radiator hoses which have molded-in reinforcement springs and reduces the I.D. from 1-3/4" to 1-1/2".