This Filter is a 30 Square Foot Filter Cartridge that Fits after some 1990 Hot Spring Hot Tubs by Watkins is 6" Outside Diameter x 10 1/2" in Length and has a 1 15/16" top and bottom hole.This fits HotSpring brand tubs only and some of these tubs have as many as 5 of these filters.
| Diameter | 6" |
| Length | 10-1/2" |
| Top Style | Open |
| Top Physical Dimension | 1-15/16" |
| Bottom Style | Open |
| Bottom Physical Dimension | 1-15/16" |
| Application | Hot Spring Spas (Watkins), Watkins Mfg/Hot Spring Spas |
| Model | Classic, Models after 1990 |
| Square Footage | 30 sq ft |
| Filbur Number | FC-3915 |
| Unicel Number | C-6430 |
| Pleatco Number | PWK30 |
| OEM Number | 31489 |
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