I liked the idea of a refillable cartridge, but found that it didn't filter quite as well as Brita. Here's a free way for you to try it for yourself! Your experience may differ from mine. The refill pack is part used.
See https://www.phoxwater.com/ for info.
Phox reusable water filter cartridge and refills (Woosehill RG41)
This offer has been gifted to someone and is no longer available.