Series 993 Reduced Pressure Zone Assemblies were produced from 1998 - 1999. Only available in sizes 4 - 6", the 993's check parts are similar to a 909 and the relief valve parts similar to a 990 with the body reconfigured for "N" shaped and "Z" shaped installations. The body was made of epoxy coated cast iron. The relief valve is of bronze construction with an external style sensing line. The 993 does have self contained check valves and replaceable bronze seats. No special tools are required for service.