Unicel Replacement Filter Cartridge 60 sf Jacuzzi Premium Spas | 6CH-961Unicel 6CH 961 Replacement Spa Filter Cartridge 60 Sq Ft (Jacuzzi Premium J 300 J 400 Style) The Unicel 6CH 961 is a 60 sq ft pleated replacement spa filter cartridge commonly used in select Jacuzzi Premium spa systems (including many J 300 and J 400 series setups). It features a 6 3 4" outside diameter body, a 15 1 2" length, an open slotted top, and a 2" male SAE (coarse) threaded bottom connection for a secure, threaded fit in compatible filter