This invention provides a valve consisting of a body and rotatable valve member, both of which are made of plastic, the valve body having a passageway intersected by a frustoconical opening which receives the valve member. The valve member is rotatable for controlling the flow through the passageway, the rotation being accomplished by engaging a recess in the outer end of the valve member. The body includes an outwardly deflectable shoulder that fits over the outer end of the valve member to hold the valve member in the body. The valve member is made to a greater major diameter than that of the opening in the valve body to provide an interference fit. Deep annular grooves around the valve opening provide a thin wall for the valve body around the opening, allowing distortion-free molding of the valve body.