Square tube ,hollow pipe,welded pipe carbon steel rectangular hollow section, good quality, lowest price Square tubeProduct nameSquare tubeSpecificationOD: 15*15mm-400*400mm, WT: 0 ... ,GB/T3091-2001Zn coating mass200-400g/m2 (glanvaized square pipe)Length of the Gi Square Pipe5.8m-12mProcessing techniqueThreading, coupling, necking, punching and so on ...