Abstract: This spool-valve distributor, comprising a pair of pistons producing opposed actions and two end covers formed with passage means for the circulation of the piston control fluid, has an assembling face formed with grooves adapted to receive a seal or gasket interposed between said face and the base member rigidly connected to the hydraulic or pneumatic device actuated by the distributor, some of said grooves being provided with lateral ribs, whereby positioning the seal or gasket on one or the other side of the relevant rib permitting of sealing said distributor body in relation to base members of different standards and dimensions.