Panasonic TK-CP21C1 Water Filter Cartridge This is the cartridge (TK-CP21C1) that came with the Panasonic pot-type mineral water purifier (TK-CP11). It has been stored unopened at home along with the main unit. It is still in the original unopened bag from when it was purchased. The water purifier itself is large, so this is an offering of the cartridge only.