Cartridge, system, and cartridge set

A system comprising:

• a case having a plurality of engagement portions;
• and
• a cartridge configured to be inserted in a first direction into the case, the cartridge including:
• a body having a chamber for storing a printing agent;
• and
• a key member located on the body at a position associated with a type of the printing agent stored in the chamber, the key member being configured to engage with a corresponding one of the plurality of engagement portions, the key member having a surface facing a second direction opposite to the first direction, the surface being configured to contact the corresponding one of the plurality of engagement portions.

A cartridge set including a first cartridge and a second cartridge, the first cartridge and the second cartridge being configured to be attached to a case having a first engagement portion and a second engagement portion, wherein

• the first cartridge includes:
• a first body having a first chamber for storing a printing agent;
• a first upper wall located above the first chamber in a height direction;
• a first supply port being open in a frontward direction when the first cartridge is attached to the case, the frontward direction being perpendicular to the height direction;
• and
• a first key member located on the first body at a position associated with a type of the printing agent stored in the first chamber, the first key member having a first engagement surface configured to engage with the first engagement portion of the case, the first engagement surface being located at the first upper wall and facing rearward opposite to the frontward direction,
• the second cartridge includes:
• a second body having a second chamber for storing a printing agent different from the printing agent stored in the first chamber of the first body;
• a second upper wall located above the second chamber in the height direction,
• a second supply port being open in the frontward direction when the second cartridge is attached to the case;
• and
• a second key member located on the second body at a position associated with a type of the printing agent stored in the second chamber, the second key member having a second engagement surface configured to engage with the second engagement portion of the case, the second engagement surface being located at the second upper wall and facing rearward opposite to the frontward direction,
• each of the first upper wall and the second upper wall has a first side to be located closer to one side of the case than to the other side of the case in a width direction and a second side to be located closer to the other side of the case than to the one side in the width direction when the first cartridge and the second cartridge are attached to the case, the width direction being perpendicular to the frontward direction and the height direction,
• the first key member of the first cartridge is located closer to the first side of the first upper wall of the first cartridge than to the second side of the first upper wall in the width direction, and
• the second key member of the second cartridge is located closer to the second side of the second upper wall of the second cartridge than to the first side of the second upper wall in the width direction.