Taiz 150cc bolt size?

[gfscoot17]

Hey guys, a bolt that secures the muffler on my taiz 150cc scooter is missing. any idea what size the bolt is? I've tried guess and check with some spare bolts and got pretty close. Its about a 5 inch long bolt thats needed, more looking for the size of the bolt then the length. Any ideas?
Thanks!

[scosgt]

Almost all China bike parts are metric. Try M8 and M10. Pick up from Ace hardware.