A couple of reasons, first,when looking at the pictures available for the ones identified as OEM versions, they are very different from the ones I have. They show a beveled top where the ones that came off my car are flat on the top and have a small relief cut on the edge. I suppose the pics may be in error, but I have been burned by a couple of the US based suppliers with supposed OEM style parts that are not close to the originals. The second reason is I recently bought a lathe for a couple of other projects and decided I might as well use this as an excuse to get more practice in. If I had confidence the available parts would have close to correct, I would have gone that route, but now the new parts are machined except for the portion I have the question about.
Jay