Stainless steel seamless U-tube Standard: ASTM, DIN, EN, GB. Grade: TP304, 316, 317, 321, 347, 310S, 314, 409, 410, 431 etc. Stainless steel seamless U-tubeStandard: ASTM, DIN, EN, GB.Grade: TP304, 316, 317, 321, 347, 310S, 314, 405, 409, 410, 420, 430, 431, etc.OD: 6-38.1mmApplication: boiler, heat exchanger, chemical industry set, shipbuilding, petrdeum set, etc.