A cartridge configured to be inserted in a first direction into a case having a plurality of engagement portions is provided. The cartridge has a body and a key member. The body has a chamber for storing a printing agent. The key member is located on the body at a position associated with a type of the printing agent stored in the chamber and is configured to engage with a corresponding one of the plurality of engagement portions of the case. The key member has a surface facing a second direction opposite to the first direction. The surface is configured to contact the corresponding one of the plurality of engagement portions.