Cal Spas Filter -  Large (394 mm)
 
This is found on most high-end or luxury Cal Spas hot tubs. 
 
Length: 394 mm Diameter: 171 mm Top: Closed/Handle Bottom: 51mm - hole/male/course thread
 
Fits Cal Spas Luxury Models - Pacifica PLUS, Tropical PLUS, Atlantic PLUS, Bel Air PLUS, Costa, Avalon, Cancun, Malibu, Baja
(unsure which model you have? Check ID plate on side of cabinet)
 
Price is for a single filter.