The 6 PCS Type VI Hot Tub Filter Cartridge by Costway is a set of easy-to-assemble spa filter pump replacements. Made from durable non-woven fabric and polyurethane material, these blue and white filter cartridges are designed to fit 4" x 3" size hot tub filters. With a medium firmness level, this six-piece set includes everything needed for assembly and is suitable for adults. Each filter cartridge weighs 1.2 lbs and is ideal for maintaining a clean and refreshing hot tub environment.