The factory replacement for SILCA Press on Disc Chucks. The 252 replace the classic SILCA 25.1 gasket after more than 20 years in the market. This unique gasket borrows from industries which require air-tight seals in the harshest of environments. The 252 gasket utilizes a high tech, full synthetic elastomer base material. It tests to a life expectancy of more than 5X the carbon filled rubber or Buna-N materials used previously. In tests with a major disc wheel manufacturer, the current SILCA Disc Wheel Adapter with 252 gasket excelled by posting a blow-off pressure of 393psi where other designs were unable to reach 120psi. Older versions of the SILCA Disc Wheel Adapter will still benefit for the new gasket, but have a lower hands-free max pressure.