... hollow section pipes and rectangular hollow section pipesSpecifications30*30-600*600 mm,30*20-600*550mmThickness3-25 mmMaterialQ235B ,Q345B,20# ,ST37,ST44,ST52,ASTM ... rectangular pipe ,400*400 mm square steel tube ,350*350 mm square steel tube ,450*450 mm square steel tube ,500*300 mm rectangular steel pipe.Other ...