SR 21in Cristal-Flo/1.5hp AG Sand Skid You won't burn many calories maintaining Cristal-Flo Top-Mount Filters. A little two-way wrist action on the control valve puts the Cristal-Flo to work cleaning itself. And, this is one workout routine you won't have to do very often. Through innovative engineering, the filter's dirt-handling capacity is maximized, which extends the time between cleanings (backwashing). Features Typical Installations ? Inground pools and water features (including fish ponds and water gardens) Quality Construction ? Durable one-piece extra-thick molded polyethylene tank Safe ? Internal air relief hole allows air to automatically escape, preventing high pressure buildup 6-Position Valve ? Allows you to perform all necessary water movement functions. A transparent sight-glass adapter is included More Choices ? Both 20" and 24" available with multi-functional 6- Position Valves. Large Drain Plug ? Large drain plug is easy to get at for removing and installing by hand or with tools if required Sleek Looks ? Contemporary style with a textured black finish that provides superior performance in all weather conditions