Vibrant Performance's BMW E36 Exhaust Manifold Flange and E46 Exhaust Manifold Flange will save you the time and high cost of getting header flanges cut when you need to fabricate a custom header or turbo manifold. This flange is cut from 3/8'' (10mm) thick Stainless Steel. The oval port sizing on these E36 and E46 exhaust header flanges is optimized for use with standard 16 gauge (0.65" wall), 1-1/2" OD tubing.