The Deringer utilizes two integral resiliently seated butterfly shut-off valves contained within a single rigid valve housing constructed entirely of 304 stainless steel. Both integral shutoff butterfly valves shall include pre-wired supervisory tamper switches contained within a weatherproof actuator housing approved for both indoor and outdoor use. Deringer Backflow Preventers with butterfly valves stop non-health hazardous pollutants from entering a water supply during backflow or back siphonage. The stainless steel structure makes these backflow preventers the strongest on the market—without a doubt. We have plenty of Backflow Preventers with butterfly valves on our site, check them out today!