[...] What I mean is that on wheels (and tires) the Diameter is always the 1st measure by default. So it seems a bit redundant having a D there. I've just checked [...] (18 months ago, Dec 5, 2022, to Catalog)
[...] Perhaps. For (Part 56903,86) it is clear from the picture that the diameter of the wheel is greater than its width/depth/thickness, so it can be inferred that 18mm is [...] (18 months ago, Dec 5, 2022, to Catalog)