Darlly 40505-2PK Spa Filter Cartridge
Replaces Unicel C-4405 · Pleatco PRB25SF-JH-PAIR · Filbur FC-2387
- Diameter × length
- 4-15/16" × 6-5/8"
- Filter area
- 25 sq ft
- End caps
- 2-1/8" open / 2-1/8" 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 40505-2PK is a 25 sq ft spa filter cartridge, 4-15/16" x 6-5/8", sold as a 2-pack. It fits the Rainbow DSF-50, Waterway Plastics, which take 2 cartridges each. It replaces Unicel C-4405, Pleatco PRB25SF-JH-PAIR and Filbur FC-2387.
Specifications
| Darlly part number | 40505-2PK |
|---|---|
| Outside diameter | 4-15/16" |
| Length | 6-5/8" |
| Top end cap | 2-1/8" open |
| Bottom end cap | 2-1/8" open |
| Filter area | 25 sq ft |
| Type | Spa |
| Cartridges per filter | 2 |
| Blue antimicrobial version | 40505M-2PK |
| Darlly description | Rainbow DSF-50, Waterway Plastics |
Cross-reference
| Brand | Part numbers Darlly 40505-2PK replaces |
|---|---|
| Unicel | C-4405 |
| Pleatco | PRB25SF-JH-PAIR |
| Filbur | FC-2387 |
| Hurricane (former brand) | HF4405-02 |
Older or other numbers that also point to this cartridge (not confirmed by a second source): PRB25SF PR (Pleatco).
Filters it fits
| Filter | Cartridges per filter |
|---|---|
| Rainbow DSF-50, Waterway Plastics | 2 (1 pack) |
Sold as a 2-pack: two 25 sq ft cartridges, 50 sq ft in all.
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-4405?
- Darlly 40505-2PK replaces Unicel C-4405. Both are 4-15/16" in diameter and about 6-5/8" long.
- What Darlly cartridge replaces Pleatco PRB25SF-JH-PAIR?
- Darlly 40505-2PK replaces Pleatco PRB25SF-JH-PAIR.
- How many cartridges does the Rainbow DSF-50, Waterway Plastics use?
- It takes 2 cartridges. Order 1 of Darlly 40505-2PK (a 2-pack) to replace the full set.
- What size is Darlly 40505-2PK?
- Darlly 40505-2PK is 4-15/16" in outside diameter and 6-5/8" long, with 25 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.