A cylinder back plate includes a frame member 11 and a cylinder clamp 12 connected to the frame member 11 by means of a pivot 13. The cylinder clamp 12 comprises a band of rigid or semi-rigid material. The cylinder clamp 12 has a retaining position with respect to the frame member 11, wherein the cylinder clamp extends substantially perpendicularly to the plane of the frame member. The frame member 11 lies parallel to a back plate of the harness or is constituted by the back plate of the harness. Thus, when the cylinder clamp 12 is in the retaining position a cylinder can be retained securely to the frame member and sliding of the cylinder relative to the frame member or back plate can be prevented. When it is desired to attach a new cylinder to the harness, the cylinder clamp 12 can be pivoted into a loading position.