A master brake cylinder comprises a reservoir and a cylinder for generating fluid pressure. Provided in the cylinder is a sliding piston, and mounted to front and rear ends of piston are piston cups for sealing a gap between the piston and the cylinder. The piston cups comprise a substrate made of rubber...http://www.google.se/patents/US5985451?utm_source=gb-gplus-sharePatent US5985451 - Elastic product
