The abstract relates to a hydraulic clutch release system, particularly for motor vehicles. The system 1 has a master cylinder and a slave cylinder, and the slave cylinder has a piston 7 which is annular in form and works inside an annular cylinder 2. The leading end of the cylinder is fitted with a seal 9 which is mounted on a one-piece seal carrier 10a through an undercut part of the carrier in which the seal fits without leaving any empty space.