The filter parts you need are available from Shepnell. They carry filter parts from all the leading manufacturers including Advantage Electric, Aqua Tech, Blue Ridge, Dynasty, Hydro, Icon, Mater, Mountain Mist and Sunrise. The spa filter cartridges are grouped into series based on the approximate outer diameter (O.D.) of the cartridge. The diameter sizes range from 2 to 10 1/16. Approximate height is determined by measuring inches from endcap to endcap. A 5% discount applies for the purchase of three or more. Other parts and accessories include chemicals, cleaners, pumps, covers and more.