Doug's Headers D371Y 1-5/8" Tri-Y Metallic Ceramic Coated Exhaust Header for Small Block Chevrolet 67-72 Thick flanges (3/8 inch to 5/8 inch) with no warping CNC mandrel bent tubes for an accurate fit and a better flow Precision formed long transition collectors that reduces backpressure Heavy gauge tubing (16 and 14G) for longer life Header tubes are pre-polished better appearance