Dimension One 1561-11 Filter Cartridge
Dimension One OEM number • 25 sq ft • 5.5″ OD × 10.9375″ long
1561-11 is Dimension One's number for this cartridge, not a part you have to buy from Dimension One. The filter itself is a 25 square foot cartridge measuring 5.5 inches across and 10.9375 inches long, and Pleatco, Unicel, and Filbur all build it. If you read 1561-11 off an old cartridge or found it in your manual, any of the numbers below drops into the same housing.
Fitment notes
The ozone cartridge for Dimension One spas, not the main filter. Its top end cap carries twelve concentric holes around a 1-15/16 inch opening, with a plain 2-7/8 inch bottom, and both sheets describe the same part. Two things to know before ordering: Unicel has discontinued its C-5402 and publishes no replacement for it, and Unicel measures the same cartridge at 11-7/8 inches long against Pleatco's 10-15/16, so measure yours. The 40 sq ft PDO40 is the longer version of the same design.
What to buy instead
Replacements for the Dimension One 1561-11
Each button searches Amazon for one of the numbers this cartridge is sold under. The OEM version is usually the most expensive of the set and the aftermarket versions are the same physical filter, so it is worth checking all of them before you order.
Every number for this filter
| Brand | Part Number | Type |
|---|---|---|
| Dimension One | 1561-11 | The number you searched |
| Pleatco | PDO25 | Aftermarket equivalent |
| Unicel | C-5402 | Aftermarket equivalent |
| Filbur | FC-3096 | Aftermarket equivalent |
Full specs, the cartridge diagram, and the complete compatibility list live on the PDO25 cartridge page. You can also see every 5.5″ × 10.9375″ cartridge if you are checking a measurement rather than a part number.
Frequently Asked Questions
What filter replaces the Dimension One 1561-11?
The PDO25 replaces it directly, and so does every cross-reference for it: C-5402, FC-3096. All of them are the same 25 sq ft cartridge at 5.5" outer diameter and 10.9375" long. Buy whichever is cheapest at the time with solid recent reviews.
Is the Dimension One 1561-11 the same as the PDO25?
Yes, physically the same filter. Dimension One 1561-11 is an OEM number, meaning it is the code Dimension One put on the cartridge that shipped with the equipment. Dimension One does not manufacture cartridges. Pleatco, Unicel, and Filbur do, and they sell the identical part under their own numbers at a lower price. Match the dimensions against your old cartridge before ordering and you are covered.
Do I have to buy the Dimension One version?
No. Nothing about the housing requires an OEM-branded cartridge, and the warranty on your equipment is not voided by using an aftermarket filter that meets the same spec. The reason to buy OEM is convenience, not performance. The reason not to is price, which is often a meaningful gap for an identical part. What matters is that outer diameter, length, and end-cap style all match.
What size is the Dimension One 1561-11?
5.5 inches in outer diameter, 10.9375 inches long, with 25 square feet of filter media. Both measurements need to land within about an eighth of an inch, and the end caps have to match so the cartridge seats correctly when you close the lid. Measure your old one rather than trusting a number that has worn off the label.
Last verified September 2026