Darlly 40121 Spa Filter Cartridge
Replaces Unicel C-4302 · Filbur FC-0183
- Diameter × length
- 4-5/8" × 4-5/8"
- Filter area
- 12 sq ft
- End caps
- Handle / 1.9" Open
Pool and spa businesses in Florida, Georgia, South Carolina, Alabama, Mississippi, Louisiana and Texas order through their Grit Game rep. Everywhere else, contact Darlly Filtration directly.
Darlly 40121 is a 12 sq ft spa filter cartridge, 4-5/8" x 4-5/8". It replaces Unicel C-4302 and Filbur FC-0183.
Specifications
| Darlly part number | 40121 |
|---|---|
| Outside diameter | 4-5/8" |
| Length | 4-5/8" |
| Top end cap | Handle |
| Bottom end cap | 1.9" Open |
| Filter area | 12 sq ft |
| Type | Spa |
| Darlly description | Pleatco skim filter, Softsider Spas, Comfort Line Spas |
Cross-reference
| Brand | Part numbers Darlly 40121 replaces |
|---|---|
| Unicel | C-4302 |
| Filbur | FC-0183 |
Older or other numbers that also point to this cartridge (not confirmed by a second source): PSS17.5 (Pleatco).
Other Darlly cartridges the same size
Same diameter and length. Check the end caps and area before swapping.
Questions
- What is the Darlly replacement for Unicel C-4302?
- Darlly 40121 replaces Unicel C-4302. Both are 4-5/8" in diameter and about 4-5/8" long.
- What size is Darlly 40121?
- Darlly 40121 is 4-5/8" in outside diameter and 4-5/8" long, with 12 sq ft of filter area.
Cross-reference checked October 21, 2026 against Unicel's 2026 Replacement Guide, Pleatco's catalog (updated September 2025), filbur.com and darllyfilter.com. A competitor number is listed only when that brand's own data pairs it with the same cartridge size. Always compare the size and end caps of your old cartridge before ordering.
Brand names and part numbers are trademarks of their respective owners and are shown only to identify compatible replacements. Darlly Filtration is not affiliated with or endorsed by them. Cross-reference by The Grit Game, Darlly's sales agency.