Doing a complete rebuild on my C36 and wanted to share the ring sizing. The top ring is 1.2mm, second ring is 1.5mm and the oil ring is 2.5mm. That is with the 91mm bore for the AMG pistons. Mercedes does not sell only rings and at $1100 per piston for some rings it’s not worth it. I ordered some from Total Seal as a custom kit for my engine so if you need some un-unobtainable rings give them a call