Roof Rack - Hole Specification

[Mazda3black]

Can someone confirm the bolt size required that secures a roof rack to the mazda. I am trying M6 standard and fine and neither seem to want to start. I also tried some inch sizes but they did not work out either.

thanks

[Mazda3black]

FYI, It was M6. I tried a different brand and it fit perfect.

[baymoe]

So what was the issue? Coarse as oppose to Fine?