An object is to provide a cartridge that is configured to be readily mountable and stir a liquid contained in the cartridge. A cartridge includes an ink pack, a first air bag and a casing provided to place the ink pack and the first air bag therein. The casing has an ink supply port, an air flow port for first air bag and an air flow port for casing that are provided on a front face of the casing in a mounting direction so that this configuration enables the cartridge to be readily mounted to the inkjet printer. The pressurized air is introduced through the air flow port for first air bag into the first air bag. This expands the first air bag to press the ink pack and thereby stir ink I contained in the ink pack.