The Pleatco PWK30 is a replacement filter cartridge listed by Pleatco for selected Watkins Hot Spring spas.
Model: PWK30
Length: 10½ inches (approximately 267 mm)
Diameter: 5⅞ inches (approximately 149 mm)
Top and bottom openings: 1 15/16 inches (approximately 49 mm)
Check the code, dimensions and end openings against your existing cartridge before ordering. Compatibility is model-specific, not universal across a spa brand.