These wrenches look like small cups or caps which fit over the canister filter and, usually, lock into place. Then, you can attach a ratchet to the wrench and remove the filter.

Sometimes the end of a filter has a hexnut in the center, so you could use a conventional wrench. If you can’t find the right size and shape cap wrench, try one of the following: • Nylon band ...

These wrenches look like small cups or caps which fit over the canister filter and, usually, lock into place. Then, you can attach a ratchet to the wrench and remove the filter.