Ace Race Parts 27006 3.500 ID 2-Bolt Exhaust Flange 304 StainlessAce Race Parts 27006 3. 500" ID 2 Bolt Exhaust Flange 304 Stainless The Ace Race Parts brand of 3. 500" ID heavy duty 2 Bolt Exhaust Flanges is machined from 1 2 inch thick 304 Stainless and will not warp when welded. Ace Race Parts Stainless Exhaust Flanges feature slotted style bolt holes for added adjustability and easy alignment. Unlike other brands that only offer 3 8 inch thick flanges, Ace Race Parts heavy duty 1 2 inch thick exhaust flanges