Double check assembly. Production began in 1998. The 1/2" assembly utilizes a bronze body. The checks are a modular in-line design. The check modules are not field repairable and must be replaced as a whole check module. The body on 2 1/2"-10" are constructed of ductile iron which is fused epoxy coated. The 2 1/2"-6" checks are a swing style and are modular in construction and made of glass filled Noryl plastic. The check disc is replaceable. The check springs are contained when the cover is removed. The 8"-10" checks are modular bronze. The check springs are contained when the cover is removed.