These are hand made, TIG welded from high quality 6061 T6 aluminum. The flanges are all CNC machined and surfaced for precise fitment and a leak free seal. Each plenum is press bent to reduce the number of welds which will assure maximum strength under high boost applications. Velocity stacks are CNC machined into each plenum bottom to improve airflow by 10-15%. The vacuum ports are placed on the underside of the plenum for a clean professional look. They are available unpolished or with a mirror like polish or powdercoated in any color you can imagine.