The Apollo RPDA-4A is a reduced pressure detector assembly (RPDA). It is available in 2 1/2″-12″ sizes and has been in production since 2011. The 2 1/2″-8″ body is made of stainless steel. The 10″-12″ body is made of ductile iron with a fused epoxy coating. The RPDA-4A utilizes either a Type I or Type II bypass.