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.

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.

Darlly 40505-2PK Spa Filter Cartridge

Replaces Unicel C-4405 · Pleatco PRB25SF-JH-PAIR · Filbur FC-2387

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. 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
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	varies

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.

Darlly 4025725 sq ft · Freeflow Spas TLX, RLX Darlly 4025825 sq ft · Freeflow Spas CLX

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.
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.

Where to buy Darlly 40505-2PK

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.

Find your Grit Game rep Contact Darlly

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.