FUSO Genuine Air Filters are made with heat-hardened glue and are built very leak resistant. Their filter gaskets are precision-made from hight grade oil-proof rubber which helps maintain their elasticity for a secure seal. Imitation filters are less resistant to leaks as they use a weaker air-dried epoxy, and their gaskets are made from general-purpose rubber. If harmful impurities is mixed into the engine oil, it will hasten oil and wear area deterioration. Extensively tested for effectiveness and durability, Genuine Air Filters help to extend the life of engines as well as improve fuel economy.