The unidirectional limiter comprises a body, each of the ends of which is provided with a connection, a closure member mounted movably between a seat and an abutment element and a throttle ring mounted rotatably on the body of the valve for modifying the section of a throttle passage which is formed in the body and which passes around the valve seat. According to the invention the seat is formed at the end of the internal sleeve member of plastics material, which is latched by axial introduction in the internal bore in the body.