Abstract: 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.

Abstract: A printing-agent container, having a container body, an outflow port, and an identifying portion, is provided. The container body has a chamber for containing a printing agent. Through the outflow port, the printing agent flows out of the chamber. The identifying portion is provided to the container body correspondingly to a type of the printing agent contained in the chamber of the container body. The identifying portion has an inner surface defining the chamber.

Abstract: A rear wheel turning mechanism in a four wheel steering system includes a rear wheel turning rod which is connected to the rear wheels of the vehicle and is adapted such that it can be displaced and thereby turn the rear wheels. An electric motor is operatively connected to the rear wheel turning rod and the steering wheel and displaces the rear wheel turning rod, thereby causing the rear wheels to turn in response to operation of the steering wheel. A rear-wheel-neutralizing spring urges the rear wheel turning rod to the neutral position in which the rear wheels are held in the straight-ahead position. A pair of clutches are interposed in series between the electric motor and the rear wheel turning rod and are adapted such that they disconnect the latter from the former, which permits the latter to return to the neutral position under the force of the rear-wheel-neutralizing spring.