Reduced pressure assembly. Production began in 1989. The 2 1/2"-10" sizes utilize a ductile iron body that is fused epoxy coated. Most hardware internal check parts are made of bronze. The 2 1/2"-4" sizes use a single check body while the 6"-10" have a split 2 piece check body design. Check and relief valve seats are replaceable. A seat removal tool is needed to change the seats. All springs are contained upon removal of check and relief covers. This unit utilizes an internal relief valve sensing line. The relief valve is able to be removed from the check body.