M10-55 10.9 bolts you can buy at a hardware store. Same for nuts. Squash the nut just a tiny bit to make it self locking.

I bought a set of 12.9 so I can get nearly full tension without self destruct. Covered in a thread on the topic.

7/16" sae grade 8 should also fit without drilling out the hole.

The aluminum side needs a washer (or nut with built in) since the bolts clamp with something like 8-10,000#.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)