Stock bolts are M10x1.5. Not exactly sure on the length. I bought replacement stainless steel bolts that were 45mm long but haven't installed them yet. Not sure why people think we need to add nuts to lock the bolts in place. The problem is the factory bolts are rusting through and failing, not that they are backing out. It won't hurt anything to add nuts, but I don't see that solving this issue.What size bolt and nut did you use?