I want to replace them when I replace my muffler, but I do not know what size they are. I want to get the new ones so that I don't have to remove the old ones, go to the store, and THEN replace the muffler. That would be illegal and very loud.

Are they a nut and bolt, or is the nut welded onto the flange upstream of the muffler?

 

They are the same size as the bolts you use to push the brake rotor away from the HUB. If you have a chilton it says it in there, I can't remember correctly. Only reason I know is because we were trying to remove the rotors and they were frozen to the hub. We drove for hours looking for them and couldn't find them. I had spare bolts that came with the carsound cat and tried that, worked perfectly. I know that chilton says m8 x 1.25" or 8mm x 1.25" or something like that. Home depot has them.