Both bolts for attaching my Perrin cat-back exhaust to the stock down pipe stripped. Anyone know what size bolts I'll need? They look like M12's, but thought I'd check here first.

These are the original bolts that came off my stock GSR. I have no idea how the hell these things stripped especially since I torqued them in by hand, then wrench, then impact.

Also just in case my weld nut on the stock down pipe is stripped. Has anyone ever attached an exhaust using a carriage bolt set up? For instance use a smaller bolt and run it thru the weld nut, then fasten with a nut on the back? Any down sides to doing this?

 

Knock out the stripped bolts with a hammer and insert new bolts from autozone or local auto store and call it a day.

 

The stripped bolts are not on the car and since they are stripped I can't bolt on my exhaust.

I've confirmed they are M12's.

 

Yup, M12. Just bought another set the other day to go with the exhaust I sold