The Vevor pool filter balls are a lightweight, reusable filter media designed to replace traditional pool filter sand. Made from 100% polyester fiber, they deliver fast, efficient filtration and help trap fine particles such as pollen, dirt, and grass clippings. These filter balls are compatible with sand filters, cartridge filters, and DE filters for versatile use. They can also be used for swimming pools, above-ground pools, fish tanks, and aquariums. A cleaning wash bag is included for easier maintenance.