💧 Darlly Filtration 81004 Replacement Filter Cartridge — 100 sq ft
This is a 100 sq ft replacement filter cartridge from Darlly Filtration, part number 81004. It measures 8″ in diameter and 16-1/2″ long, with a handle top and a 3-5/8″ open bottom. It uses 3 oz filter media. If your old part carries one of the cross-reference numbers further down, this is listed as its alternative.
📏 Specifications
| Specification | Value |
|---|---|
| Brand | Darlly Filtration |
| Manufacturer part number | 81004 |
| Bottom Physical Dimension | 3-5/8″ |
| Bottom Style | Open |
| Diameter | 8″ |
| Length | 16-1/2″ |
| Media Type | 3 oz |
| Square Footage | 100 sq ft |
| Top Style | Handle |
| Catalog description | Cartridge, 100sqft, ht, 3-5/8″ob, 8″dia, 16-1/2″L, 3oz |
🛁 Spa makes it is listed for
Caldera Spas (Watkins), Watkins Mfg/Caldera Spa.
🔄 Cross-reference part numbers
These part numbers are listed as alternatives for this part.
| Brand | Part number |
|---|---|
| Filbur | FC-3965 |
| Filbur | PC-3965 |
| Pleatco | PCD100W |
📐 How to check the size
Measure your old cartridge from end to end for the length, and across the pleats at the widest point for the diameter. Then check the hole in the center of each end cap: an open end has a hole straight through, a closed end is solid. All of these should match the specifications table above.



