The 3" Wilkins 375AST Reduced Pressure Zone began production in 2011 and is still currently in production. The 375AST uses grooved fittings between the backflow and valves. Stainless steel body has a single victaulic style cover houses both plastic cam checks and a plunger style bronze relief valve hangs below. An external sensing line pressurizes the diaphragm. Self contained cam checks are held in place by plastic retaining rings. Use caution when servicing as retainer rings often snap. No special tools are required for servicing.