Replacement filters

Find your cartridge by size

Most housings take a 10" or 20" cartridge in a Standard or Jumbo width. Two measurements of your old cartridge will tell you which one you need.

How to tell the size

Grab your old cartridge and a tape measure. Length and width are all you need for housing cartridges.

Measure the length

Measure end cap to end cap. About 250 mm is a 10" cartridge. About 508 mm is a 20".
Measure the width

Measure straight across the end cap. About 63 mm is a Standard size. About 115 mm (4.5") is a Jumbo, often called Big Blue.
Check the ends

Fittings on the ends instead of an open centre usually mean an inline or quick connect cartridge. Those are matched by the code on the cartridge or your filter model, not by size.
Match the size first

A cartridge only works properly in the right housing, so get the size right before you pick sediment or carbon. Most cartridges also have a code printed on them, which is the quickest way to find a match.