The seal utilizes a high tech and very red, fully synthetic elastomer base material rather than a carbon black filled natural rubber of previous seals. This unique bright red seal borrows from industries which require air-tight seals in the harshest of environments, and 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 seal slips onto the valve stem with a satisfying \'click\', while unique internal geometry actually utilizes line air pressure to compress the seal onto the valve stem: the higher you pump, the harder it grips the stem! This design is so iconic we\'ve found more than 20 companies world-wide making pump heads and seals copied from this, but none of them can come close to the precision and technology in our new seal. Key Features: Fully Synthetic Elastomer Base Material 5X the durability of traditional rubber materials New Two-Stage sealing geometry optimized for all Presta valve stems Pressure amplifying dome geometry uses air pressure to clamp valve stem Fits all prior SILCA Presta heads Made in USA