The left-hand or right-hand models of the QP series pneumatic disc brakes are distinguished by the installation direction of the air bladder (air chamber).

Left-side installation: The air bag is located on the left side of the brake.

Right-hand installation: The air bladder is located on the right side of the brake.

For instance, the model QP12.7-A-6-L indicates the gas bag is installed on the left, whereas QPL12.7A-B-E1-R signifies it's installed on the right.