SILCA’s new high-tech elastomer 252 gasket replaces the classic 25.1 gasket. Capable of fitting in any SILCAdisc adapter but optimized for use in their new aluminum Disc Adapter or the Hiro.
From SILCA:
NOTE: Compatible with all prior SILCA disc adapter designs, however, the limited height in the adapter head will prevent the valve stem from fully engaging the gasket. Generally the 252 gasket in a CP1 will hold a minimum 120psi on any size or type of valve stem, while it will hold 70-80psi when used in older SILCA adapters.