SILCA ELASTOMER SEALThe Silca Elastomer Seal has a fully synthetic elastomer base material and has 5x the durability of traditional rubber materials. There are several different types of gaskets and some have a two-stage sealing geometry that is optimized for all Presta valve stems. Compatibility254: Hiro V. 2 locking presta chuck323: Art. 24. 4, Art. 84, Art. 323, Silca Impero frame pump heads242: 30. 0/30. 2, 17-4 stainless Presta only chucks252: Silca disc adapters | Silca | Elastomer Seal Hiro V. 2, #254 | Rubber