Compatible ModelG52 Backup Valve Case fits Zodiac Polaris models 180, 280, 380, 480 PRO, 3900 Sport, Vac-Sweep 380, Vac-Sweep 280, 280 TankTrax. Upgraded VersionCompared with the previous backup valve, our g52 backup valve replacement kit for polaris has upgraded the shell material, high strength proprietary crack resistant polymer construction, will not be easily damaged, and has twice the life span. G53 Gear MechanismMade of friction-resistant and stable POM material. Pom has a very low coefficient of friction and good geometric stability, especially suitable for the manufacture of gears and bearings, this material is more able to withstand high water pressure operation. FunctionThe Upgraded Version will solve the issue when your pool cleaner is stuck on an obstacle, although your backup valve is still open, water will no longer be sprayed from the nozzle, and keep the water out.