I am the manufacture for square and rectangular steel tube.Our products using in construction structure home and abroad wildly. Commodity Square and rectangular steel pipe Specifications 30*30-500*500 mm Thickness 3-25 mm Material Q235B ,Q345B,20# ,ST37,ST44,ST52,ASTM A53, ASTM A 106 and so on Standards GB/T3094-2000 or JISG 3466 GB/T6728-2002 and so on Payment terms L/C or T/T package Wrapped with steel strips or as customer's requirement Contact Jack Li :8613653375788;86-0317-3099705