Bolts / nuts

[NORRO]

I know this subject has been thrashed to death, but even after trawling through 25+ pages on here i cant seem to get a definite answer.

I am having an unsilenced Supersprint b pipe fitted to an aftermarket back box on Monday.
I purchased some new OEM bolts and springs from Honda [at no great cost] but from what i can gather, the bolts are not quite long enough for the job.

It seems that a few of you on here simply pop along to your nearest B&Q and get bolts from there.
What size/length bolt do i require ? I will be using the springs, but I have seen M8, M10 and M12 mentioned, so which is it ?

Also which size for the b pipe to the Cat ?

Thanks in advance.

 

[Shaenei]

Just measure the diameter of the bolts you've bought

I don't think you'll be able to get the bolts for the cat - bpipe joint, I don't think b&q etc stock bolts with the round heads with 2 flats that the OEM bolts have