Butterfly valves are composed of two semi-circular plates hinged on a common spindle. Butterfly valves are widely used because of their capabilities to shut off flow immediately, and allow constant, regular flow. Butterfly valves permit flow in one singular direction only. Materials: Body: PVC Seat Seal: EPDM Stem: 410 Stainless Steel O-Ring: EPDM Handle: ABS Spring, Pin, Bolt: 304 Stainless Steel