A valve formed of a body having a flow passageway therethrough defining an annular valve seat, a valve disc member positioned in the flow passageway movable between a closed and open position, the disc having a peripheral sealing surface which engages the valve seat when the valve is closed and a valve stem axially and rotatably received in stem openings in the valve body, the stem extending within the flow passageway, the valve disc being between the stem and the valve seat and boss portions having slots therein extending from the disc rearward surface to either side of the valve stem, each boss portion having aligned upper and lower slots in parallel planes intersecting the plane of the disc sealing surface at an acute angle, and pin members extending from the stem received in the upper and lower slots so that when the pin member is axially displaced the disc is moved to and away from the seat and when it is moved away from the seat, the disc may be rotated without contacting the sealing ring to open the valve allowing fluid flow therethrough. The disc is supported to the stem in such a way that in all positions the plane of the disc sealing surface is parallel the axis of the stem.