COMP Cams offers a complete line of valve stem Seals, from the stock GM O-Ring to the positive-stop PTFE Seal. These Seals are a must to keep unwanted oil from entering the combustion chamber through the clearance in the valve guides. The O-Ring Seals use the standard retainer and oil splash shield. The umbrella Seal is normally used when a larger-than-stock diameter spring is used, in the case of a double spring, the positive-stop PTFE Seal is used. We also have a smaller diameter Viton Seal available for triple spring Applications.