Smooth connection between flange and pipes. The interior of the flange is welded in a circle and polished,NO welding slag. Sensor position not protrude inside surface. Flange thickness we used are 10mm,12mm and 15mm. The deformation coefficient of the flange surface within 0.5mm. TIG weld make sure the firmness and gilding surface. Inside of pipe head polish 5cm,achieve better air flow and sound. Exhaust bellows use crochet net transverse,reducing vibrate frequency. Beautiful surface finish,polish or brush.coating blue.coating yellow.coating purple and original color.