Stainless steel seamless U-tube Standard: ASTM, DIN, EN, GB. Grade: TP304, 316, 317, ... , 347, 310S, 314, 409, 410, 431 etc. Stainless steel seamless U-tubeStandard: ASTM, DIN, EN, GB.Grade: TP304, 316, 317, 321 ... , chemical industry set, shipbuilding, petrdeum set, etc. Stainless steel seamless U-tube