Universal Block Hugger Header: BBC 396-454, Tube Size 1.75", Collector Size 2.5" FLOWTECH Block Hugger headers are ideal for hot rods where fit and finish is really important. Block Huggers make performance and style easy for engine swaps, and with our new Hugger Toobs you can hook up to an existing exhaust system with ease. Features: Computer-controlled mandrel-bent tubing for smooth exhaust flow Sturdy 16 gauge tubing Tight-tuck design for narrow frame rails Easy installation - can be used with stock motor mounts Precision die-cut exhaust port flanges Engineered and tested for a leak-proof seal All necessary hardware included for a complete installation Bolt Size 3/8-16 x 3/4 Brand Flowtech CARB (California) Compliant No Collector Diameter 2.50 inch Emission Code 4 Engine Big Block Chevy Header Finish Black Paint Header Style Block Hugger Primary Tube Dia. 1-3/4 inch Product Type Headers Tube Material Mild Steel UPC 787480110305 Part Number 11030FLT