Abstract: A piston is mounted for relative sliding movement in the cylindrical bore of a sleeve. The piston comprises a plurality of piston parts, one, a driving piston part connected with a prime mover or a fixed support. A piston rod, supported by the piston at one end and by a sleeve guide at the other end, drives said driving piston part. The other and driven piston parts are connected with, and driven by said one piston part through a metallic ball, rollable in a groove formed in abutting piston part surfaces. This groove extends generally parallel to the piston axis, at an angle thereto, and with the opposite end groove portions thereof closest to the piston axis. When the piston parts move in given and opposite directions, the depth of the groove reduces and the ball functions to transmit motion from the driving piston part to the driven piston part. When the piston parts move in the other direction, the depth of the groove increases and no motion is transmitted.