A square baler having a baling chamber of which the side walls are movable by respective hydraulic cylinders. The supply of hydraulic fluid to and from the two hydraulic cylinders is effected by a common control circuit that ensures that the two sides walls are displaced in synchronism with one another by equal and opposite amounts.

A baler implement includes an upper compression panel and a first side compression panel both partially form a compression chamber. A compression frame is attached to a main frame. The compression frame is disposed adjacent to the upper compression panel. A first upper pivot link contacts the upper compression panel and is rotatably coupled to the compression frame for rotation about a first upper link axis. A first side pivot link contacts the first side compression panel and is rotatably coupled to the main frame for rotation about a first side link axis. A first actuator interconnects the first upper pivot link and the first side pivot link. Retraction of the first actuator simultaneously moves the upper compression panel in a first vertical direction along a first compression axis and the first side compression panel in a first horizontal direction along a second compression axis.