Material are hot rolled steel coils.Hot rolled steel strips.Q195 Q235 Q355 are main material of square tubes.Q195 = S195 / A53 Gr. AQ235 = S235 / A53 Grade B / A500 Gr. A / STK400 / SS400 / ST42.2Q355 = S355JR / A500 Grade B Grade CThe standard ASTM A500 ASTM A53,Grade A,Grade B,Grade C.