The product is manufactured by cold-drawn method to form special-sized internal spiral ribs in the inside wall thickness. Each tube is inspected by eddy current testing and ultrasonic testing prior to the final transformation. Heat-treatment in the controllable atmosphere furnace ensure the tube stable property and workmanlike finish.The specification we can supply is: OD:31.75~63.5mmWT:4.5~13mm The steel grade we can supply is as follows, The specification we can supply is as following picture, The products are suitable for making high-pressure boiler to improve the efficiency by preventing the forming of steel film.