work passages 46 and 48 while preferably walls 54 are slightly 34 underlapped 34 relative to the size of the openings for purposes of stability as is well known equal minimal fluid flow in and out of chamber 16 occurs in this position of control member 50 to hold piston 18 at rest upon energizing actuator 58 in one manner control member 50 is pivoted such that the cup elements 52 shift laterally relatively leftwardly to the position illustrated in fig1 in this second position the work passage 48 is in open communication with internal cavity 36 while the other work passage 46 communicates with exhaust passage 44 via both fluid transfer zones 56 pressure fluid from inlet port 24 enters the right hand chamber 16 to shift piston 18 leftwardly the fluid displaced from the left hand chamber 16 returning to reservoir 12 through the fluid transfer zones 56 in this position it will be apparent that the work passage 46 and return passage 44 constitute a pair of fluid passages which are selectively interconnected via fluid transfer zones 56 similarly upon opposite operation of actuator 58 control member 50 may be shifted oppositely from its neutral fig3 position so as to interconnect the pair of passages 44 and 48 through fluid transfer zones.