Back box bolt size - NC

  1. My model of MX-5 is: 1.8 NC (2008)
  2. I’m based near: London
  3. I’m looking for technical help or recommendations on: I have the Klarius mid pipe repair piece for the NC, and I need the bolts that go between the mid pipe and the backbox.

The hole in the Klarius is about 13.5mm, so M12 is the largest bolt size available but everywhere I look seems to suggest they are M10. So I am wondering if the hole in the OEM backbox is M10 but klarius are just larger.

Given my only local option (and quickly) is to buy a bag of them. I would rather have the right one, any ideas if it’s M12 or M10? I have M10 here and the head doesn’t go through.

Have a look in the link below.
Are the bolts/studs still in the OEM back box flange

Thanks it definitely looks like m10 x 25mm, mine are 40mm so that will be fine. Mine I suspect are studded and will need to be drilled out (seems to be the common theme on these)