6 studs per bezel, and no, they are not machine thread, they are threadless and rely on the pal nut cutting in to the smooth post. That idea works OK when originally installed, but after on and off a few times, and rechroming, not so well !!

The other issue is the bezel is the only thing that secures the actual tail light housing to the rear panel of the car, so it needs to be held pretty tight. If it were just the bezel, like mentioned above the pal nuts with the sealer in them would probably hold the bezel a lone fine.

I did pick up some these, which I will probably hav to end up using. I was hesitant about using them though as once they are on, removing them in the future would be a major pain. That being said, doubt they would ever have to come out again.

http://www.aaronspushnuts.com/tinnerman_spring_nuts.htm