Zhejiang Guanyu Steel Tube co., Ltd. specializes in stainless steel seamless tubes and pipes. Our Grades are 300 series especial in special grades including Duplex Steel (S31803 and 2205 ),317L, 347H, 904L , and our main products include stainless and carbon steel pipe fittings, flanges and valves which are often used in the chemical and petrochemical industry, ship building, and fabrication of boiler & heat exchanger.