I bought a new Brita Aluna Water jug a couple of months ago. According to the Brita guide, both Maxtra and Maxtra+ cartridges are compatible with this model, which mean't I could use the existing cartridges I had from my old Brita model. This is rubbish....... !!! do not believe the guide. No way any maxtra cartridge will work because Brita have changed the design of the outlet valve! I am having real trouble finding cartridges that will fit and work, and seriously considering changing to a filter jug from a supplier that does not con its customers. Thanks for nothing Brita