This unique bright red gasket borrows from industries which require air-tight seals in the harshest of environments. It tests to a life expectancy of more than 5X the carbon filled rubber or Buna-N materials used previously. New Two-Stage seal geometry seals on both valve stem and at the base of valve core threads resulting in a more positive seal and improved durability. The new gasket slips onto the valve stem with a satisfying 'click', while unique internal geometry actually utilizes line air pressure to compress the gasket onto the valve stem: the higher the pressure, the tighter the seal. This design is so iconic we've found more than 20 companies world-wide making pump heads and gaskets copied from this, but none of them can come close to the precision and technology of the SILCA 242.