My guess is these caps are being made for a totally different purpose, but someone in Australia has discovered that they look similar to the old Rover hub caps and are selling them as a substitute.
If these kits come from various Chinese sources, this tends to suggest that some Chinese factory must be making those red caps. They probably make more than one kind of cap. I wonder if the caps could be purchased separately? I guess the big problem with anything from China is they generally have minimum orders of 1000 or more, which makes the whole idea of importing them impractical. Even at 10 cents each, that is a lot to pay for a lot of caps! But if they could make their caps a smidgen deeper and out of slightly softer materials, they would pop on and tend to clasp the nut and washer.
