Series 919 Reduced Pressure Zone Assemblies began production in 2003 and are still manufactured. The devices are available from sizes 1/4 - 2" and are constructed of bronze. The 919 features two covers that thread into the body and a seperate relief valve cover that uses 4 bolts. The check assemblies are not self contained and the springs push pressure against the covers, caution should be taken when servicing. No special tools are required for service.