Thanks for the great advice, I thought maybe someone might know off the top of their head... I know the backs are bit longer than the front.

When I figure it out I will throw on here for future reference with part numbers. :D

For pictures, see - BMW E70 X5 xDrive48i N62 4.8L Exterior Body Fender Flares - 51770421056 - Wheel Arch Extension Kit - ES#130853

Yeah, sorry I don't have the count and would have to do the same thing you would - go count them. I kind of think it is 10 of each, but I wouldn't bet on it -- but if you buy 20 of each I'm pretty sure you'll have some spares. And they're cheap.

What up fellas!

I got my new/used arches this evening, so I was able to count how many rivets I will need. The magic numbers are:
Fronts- 9 on each side (18) PN:07142151750
Rears- 7 on each side (14) PN: 51777171004

... better get a couple of extra ones of each type, just in case.

Thanks, I thought about that. I would hate not to complete the job because I busted a few. :thumbup:

from the horse's mouth
 

Rivets, with car models and rivet counts.

Front/rear:
parts.bmwmonterey.com/p/BMW__/EXPANDING-RIVET/43796445/51777171004.html

Rear:
parts.bmwmonterey.com/p/BMW__/Blind-rivet/43778186/07142151750.html

Cheers,
Matt