The 3" Wilkins 375 Reduced Pressure Zone began production in 1998 and is still currently in production. Epoxy coated cast iron 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.