The 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 Coated Ductile Iron Units (10” And 12”) Are Easily Maintained in The Line Without Any Special Tools. The Triforce™ Check Valves Operate With a Spring Assist in The Flowing Condition to Provide Excellent Flow Rates Which Are Documented by an Independent Laboratory. | Apollo-Conbraco | 4ALF20G03