Abstract: The present invention relates to an assembly, for use in a pressurized fluid mechanism equipped with pistons bearing against a reaction plate by way of slipper blocks, which assembly consists in such a piston and the associated slipper block coupled to one end of said piston by means of a "ball and socket" type assembly, the male element of the assembly being constituted by that part of the slipper block facing the face supporting the said slipper block on the reaction plate. A bolt comprising a screw and nut, joins the slipper block to the piston, the supporting surfaces of the nut and of the screw head on the corresponding parts of the slipper head and of the piston being of the "ball and socket" type.The invention finds an application in the production of high power hydraulic motors.