The mechanical structure component can be welded, riveting, boilting, and used as frame, bridge, construction and etc. The product specification: GB/T12770-1991,ASTM A500 ,A513,A519 Specification: Square Tube:0.5"x0.5"~4"x4" Rectangle Tube:0.625"x0.375"~5"x3 " WT: 0.03"~0.237" Length:13.1'~40'.