4ALF20003 (Apollo-Conbraco) | 3 Inch | 4ALF-200 RP With Osy Gates | Flanged X FlangedThe Apollo Model Rplf 4A Lead Free Reduced Pressure Principle Backflow Preventers Consist of Two Independently Acting, Triforce Center Stem Guided Check Valves With a Differential Pressure Relief Valve Located Between The Check Valves. The Unit is Designed to Give Maximum Protection Against Backflow of Health or Non Health Hazard Fluids by Either Back Pressure or Back Siphonage. The Durable Domestic Stainless Steel Units (2 1 2 8) And The Fda Epoxy