One part here is listed as replacing Absco® shed door rollers: a 22mm adjustable shed door carriage and roller, which also covers Heritage™ and Span Built™ shed doors using the same fitting. On a shed slider the carriage is the only moving part, and it is what fails. The roller flattens, the wheel seizes on its pin, or the adjuster thread strips, and the door then drags on the bottom track or lifts out of the top channel while the sheeting and frame are still fine. The 22mm in the title is the identifying dimension. Take the old carriage off the door, measure the wheel across its face, and check the bracket’s fixing hole spacing before ordering, because shed doors of similar size use several different carriages.