What is the Darlly replacement for Unicel C-5431?

Darlly 50301 replaces Unicel C-5431. Both are 5-1/8" in diameter and about 10-1/4" long.

What size is Darlly 50301?

Darlly 50301 is 5-1/8" in outside diameter and 10-1/4" long, with 30 sq ft of filter area.

Darlly 50301 Spa Filter Cartridge

Replaces Unicel C-5431 · Filbur FC-3910

Darlly 50301 is a 30 sq ft spa filter cartridge, 5-1/8" x 10-1/4". It replaces Unicel C-5431 and Filbur FC-3910.

Specifications

Darlly part number	50301
Outside diameter	5-1/8"
Length	10-1/4"
Top end cap	1-15/16" Open
Bottom end cap	1-15/16" Open
Filter area	30 sq ft
Type	Spa
Darlly description	Hot Springs Spas/Watkins Mfg.(Model FH/IH(220 volt))

Cross-reference

Brand	Part numbers Darlly 50301 replaces
Unicel	C-5431
Filbur	FC-3910

Older or other numbers that also point to this cartridge (not confirmed by a second source): PWK30-220V (Pleatco).

Questions

What is the Darlly replacement for Unicel C-5431?: Darlly 50301 replaces Unicel C-5431. Both are 5-1/8" in diameter and about 10-1/4" long.
What size is Darlly 50301?: Darlly 50301 is 5-1/8" in outside diameter and 10-1/4" long, with 30 sq ft of filter area.

Where to buy Darlly 50301

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 Darlly 50301 on darllyfilter.com

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.