WARNING – Special care should be taken when coupling Shields series 331, 337 and 368 EPA approved barrier fuel hoses. Always use a lubricant when inserting a fitting. Oil based or other lubricants designed for rubber or plastic assembly should be used. Silicone is not recommended as it may cause coupling retention issues. Over-sized fittings should not be used. The fitting should slide into the hose with minimum, but some, resistance. Using fittings with oversized barbs may result in damage to the barrier layer. Sierra recommends the use of Oetiker stepless ear clamps or worm drive clamps to attach the fuel hose. Do not use wire ties or spring tension clamps. Over-tightening a worm drive clamp may result in damage to the inner layer and cause fuel to get in between the layers. This will cause the layers to separate and block the flow of fuel.