1-1/2" tubing primarytubes, these headers will not work on Jeep TJ's Our header flanges are 3/8" thick and all of our primary tubes are constructed with 16 gauge tubingand a 2.5" slip type collector.Each design is available in either a ceramic finish or a non-plated (black) version. Our written guarantee states that if the headers do not fit your engine conversion exactly as you see fit, then simply return them for a full refund. You will only be responsible for the freight charges. We do not warranty the chrome plating on our exhaust systems, and the use of aftermarket header wrap products will void the header warranty. Thirty-four years of continual fine tuning and adjustments have made the Advance Adapters headers a choice for all engine conversion installations. The Chevy Gen III headers use the stock flange gasket and metric bolts (Not Included). We can provide two collector rings for the exhaust shop and the collector gaskets. These are sold separately and found under p/n 717514.