I built my diffs in my new kit. the diff shims that came with my kit were silver and the same size as the package of new diff shims that i had. the new package of shims i had were black and seemed to be about .05mm thicker and seemed to have a lot less flex when i tried to bend them compared to the ones that came with the kit. i dont understand why there are different runs of shims. the ones that came with my sct410 have been bulletproof. over two years on them and they still look good.