Hi-Tech 10inch 2.5 dia PP filter are Manufactured from 100% Pure Polypropylene – Designed for purity and chemical compatibility – Spun fibers form a true gradient density from outer to inner surfaces – NSF Certificated Hi-Tech P.P is manufactured from pure100% polypropylene fibers. The fibers have been carefully spun together to form a true gradient density from outer to the inner surface. The cartridge is designed for purity. They will not impart taste, odor or color to the liquid being filtered when used within the recommended temperature limit. Additionally, the polypropylene construction provides superior chemical resistance and is not prone to bacterial attack. The coreless strength of the cartridges achieved by sintering the many fibers into a solid matrix