Our hot tub spa filters meets or exceeds manufacturer specifications.
Filter Specifications:
- Square Footage: 8.5 sq. ft.
- Media/Thickness: 3
- Diameter: 2-7/8"
- Length: 17-1/16"
- Top: 2-1/8" Hole
- Bottom: 2-1/8" Hole
Equivalent to:
- Pleatco: PRB8.5
- Darlly: 20191
- Unicel: C-2303
- Filbur: FC-2324
- OEM: 17-0052
This Filter Fits The Following Brands:
Pentair, Rainbow Chlor, Emerald, Cygnus, Conway
Filter Glossary

As you can see in this graphic, when looking at a filter's threads from the side the difference is very obvious. Standard, sometimes called "MPT" or "Male Pipe" threads are smaller and have a higher number of threads than the S.A.E. style. The S.A.E. threads are large and are square in nature almost resembling a child's toy.
- MPT: Male Pipe Thread
- FPT: Female Pipe Thread