Pro Series high-rate sand filters are the very latest in pool filter technology. Molded of durable, corrosion-proof reinforced thermoplastic, Pro Series filters feature an advanced, self-cleaning lateral under drain system for smooth, efficient flow and totally balanced backwashing. Pro Series sand filters also feature a self-cleaning 360-degree slotted lateral for totally balanced flow and backwashing. Their integral top diffuser ensures even distribution of water over the top of sand media bed with full size internal piping for smooth, free-flowing performance. So for crystal clear water with only minimal care, pool professionals choose Pro Series. Note: Filter includes 1 1/2" Vari-Flo Valve.