The one on the left looks like a standard item, on a steel plate (try a magnet) and the one on the right is a Surflex carbon item. The Surflex is an upgrade over stock. Higher friction material, so able to handle more HP. The Surflex pack usually builds with thinner steels so you can 8 or 9 plates in to increase the surface area of friction material to.
That would explain why I had 8 rather than the standard 7 plates. Cheers Nelly
