Abstract: A valve including a cylindrical bore having a circular seat at one end thereof, a valve member that is movable in the axial direction of the seat, and control means connected to the valve member, the valve member including a first portion which serves as a closure element, and a second portion which is engaged in the bore and which is shaped to regulate the flow of the fluid at a desired rate depending on the axial position of the valve member, the second portion of the valve member is detached from the first portion and has a cylindrical outside surface of diameter such that it is in sliding contact with the cylindrical surface of the bore; at least one recess is formed in the cylindrical outside surface of the second portion of the valve member so as to define a passage having a predefined shape, and means is provided for permanently holding the two portions of the valve member in mutual contact so that they are displaced axially simultaneously under the action of the control means.