The PolyPropylene – PP filter cartridge Housing is made of ruffed reinforced polypropylene. They are suggested for low flow rates to higher flow rates in extensive range of applications including residential, business and industrial sectors. Available in 8″, 10″, 20″ Standard models and 10″, 20″ Jumbo models for higher flow rates. Optional Pressure of PP Filter Cartridge Housing – reliefbleed button on inlet side of cap. Thick walls for increased strength.