This is a replacement for the Sundance Spas Micro Clean filter cartridge and is used in conjunction with the C-8380 75 sq ft pleated filter cartridge - SC722
This micro clean filter cartridge is disposable (cannot be cleaned) and must be replaced every 3-4 months to ensure proper spa filtration and equipment operation.
Sundance Spas Part No. 6540-502 use with 6540-501