Abstract: A master cylinder in which the piston and push rod, connected with an open ball and socket arrangement, are retained in the master cylinder bore and held in the requisite inactive piston stop position by a retainer. The retainer is a generally U-shaped wire clip which extends through a pair of parallel through-bores in a plane perpendicular to the master cylinder bore axis. The through-bores are spaced apart sufficiently far to permit the retainer to receive the smaller rod portion of the push rod between the retainer legs. They also intersect the master cylinder bore chordally so that they are engaged by the push rod ball end when the master cylinder is released. An internal groove in the master cylinder bore adjacent the bore open end has chamfered side walls which prevent damage to the master cylinder seal lips when the master cylinder piston is assembled in the bore.