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.