6" × 8-1/4"
Bullfrog spa filters
Bullfrog has used both threaded top-load cartridges and, on later spas, a coreless cartridge design. The threaded 8" cartridges come in a short-thread and a long-thread version, and the Pleatco catalog dates those to different production years, so the thread on your old filter matters.
Coreless cartridges have no Unicel equivalent in the 2026 guide and are listed here by their Bullfrog and Pleatco numbers.
This page lists 7 Bullfrog replacement cartridges from the Unicel 2026 Replacement Guide, the Pleatco 2023 catalog, the Filbur catalog and manufacturer and retailer pages, plus model and model-year fitment for 3 of them (5 hot tub models in total). 4 have a Filbur number. Find your spa filter by the OEM part number on the end cap, or measure it and compare sizes below.
Clean and replace intervals for one cartridge on this list, plus the cross-reference numbers and a buy link: filter replacement schedule and reorder.
- 6CH-9406CH-940, 6" (152 mm) × 8-1/4" (210 mm)See replacement
- 10-10358CH-950, 8" (203 mm) × 6" (152 mm)See replacement
- 10-28708CH-951, 8" (203 mm) × 5-3/4" (146 mm)See replacement
- C-4335C-4335, 4-15/16" (125 mm) × 9-1/4" (235 mm)See replacement
- C-4950C-4950, 4-15/16" (125 mm) × 13-5/16" (338 mm)See replacement
- 10-00281not listed, 6-5/8" (168 mm) × 6-1/4" (159 mm)See replacement
- 10-00282not listed, 8" (203 mm) × 6-1/4" (159 mm)See replacement
| Cartridge | Unicel | Pleatco | Filbur | Size | Fits | Status |
|---|---|---|---|---|---|---|
| 6CH-940 (Bullfrog Spas) | 6CH-940 | PWW50P3 | FC-0359 | 6" (152 mm) × 8-1/4" (210 mm), 50 sq ft | not listed | verified |
| 10-1035 | 8CH-950 | PBF35 | FC-0536 | 8" (203 mm) × 6" (152 mm), 50 sq ft | not listed | verified |
| 10-2870 | 8CH-951 | PBF36 | not listed | 8" (203 mm) × 5-3/4" (146 mm), 50 sq ft | 1 model | verified |
| C-4335 (Bullfrog Spas) | C-4335 | PRB35-IN | FC-2385 | 4-15/16" (125 mm) × 9-1/4" (235 mm), 35 sq ft | not listed | verified |
| C-4950 (Bullfrog Spas) | C-4950 | PRB50-IN | FC-2390 | 4-15/16" (125 mm) × 13-5/16" (338 mm), 50 sq ft | not listed | verified |
| 10-00281 | not listed | PBF17 | not listed | 6-5/8" (168 mm) × 6-1/4" (159 mm), 18 sq ft | 1 model | verified |
| 10-00282 | not listed | PBF40 | not listed | 8" (203 mm) × 6-1/4" (159 mm), 30 sq ft | 3 models | verified |
Know your model but not the part number? See Bullfrog filter by model and year.
3 of these rows do not have enough detail for a stand-alone page (for example, no OEM number or no second cross-reference), so their pages are kept out of search results and this table is the main reference for them.
Brands that share cartridges with Bullfrog
- Caldera, same part numbers C-4335, C-4950
- Sundance, same part numbers C-4335, C-4950
- Waterway Plastics, same part numbers 6CH-940, C-4950
- Beachcomber, same part number C-4950
- Cal Spas, same part number C-4950
Guides that apply to Bullfrog
- Bullfrog threaded and coreless filters
- Open-end vs threaded hot tub filters
- How Filbur, Unicel and Pleatco numbers compare
- How to find your spa filter size
- How to install a cartridge
- All guides
Search Bullfrog part numbers on Amazon
Each button opens an Amazon search for that part number. The cartridge page is where the cited size and fittings are. Match those before you buy.
Part numbers from this table
-
6CH-940 cartridge -
8CH-950 cartridge (OEM 10-1035) 8" × 6"
-
8CH-951 cartridge (OEM 10-2870) 8" × 5-3/4"
-
C-4335 cartridge 4-15/16" × 9-1/4"
Disclosure: we may earn a commission from qualifying purchases made through retailer links on this site, at no extra cost to you. As an Amazon Associate I earn from qualifying purchases. Amazon links on this page go to Amazon.com and are affiliate links; they never change what we write, and the list is not ranked by commission. Each “Search on Amazon” button opens an Amazon search for the part or product name shown, not a single listing we pre-checked. Check size, quantity and your spa maker’s guidance before you buy. See our affiliate disclosure.
Model-year fitment comes only from the sources named on each cartridge page. Where no source lists models or years, the page says so.