1.high rate sand filter 2.durable corrosion-proof polymeric material 3.unitized tank 4.DN:22.05"-35 ... in pool filter technology. Molded of durable, corrosion-proof polymeric material, they feature attractive, unitized tank construction for years ... servicingUnitized, corrosion-proof filter tank molded of rugged, colorfast polymeric material for dependable, al-weather performance7 position Hayward Vari- ...