A replacement filter cartridge assembly for hot tubs, spas and other aquatic environments includes a top end cap, a bottom end cap, a perforated elongated core extending between the end caps, and a pleated filter medium situated between the end caps and disposed circumferentially about the core. The...http://www.google.com/patents/US7416663?utm_source=gb-gplus-sharePatent US7416663 - Replacement filter cartridge assembly having an internal lock ring
