The Hersey 6CM RPDA is a reduced pressure detector assembly ( RPDA ). It was available in 4” – 10” sizes and was produced from 1991-2004. The body was made of either bronze or cast iron with a fused epoxy coating or galvanized coating. The repair parts for the bronze and cast iron devices are different. The 6CM RPDA utilized a 1 ½” FRP II for the bypass assembly.