I use an aluminum 2" 3 bolt flange gasket for my downpipe. You can buy them at advance autoparts or anywhere that sells domestic stuff, adn it's reuseable......and it doesn't leak. the bolts can be found at any good hardwre store. replace them wiht grade 8 bolts. if you replace it with a regular stud from a hardware store, you could be in for a rude awakening (believe me, I know)