thick wall big rectangular and square tubes 1. max wall thickness 40mm 2. max OD ... 4. max lenghth 15meters 5. special sized can be ordered1. square Steel Tubes min size: 30*30mm, thickness: 2-6mm, ... mm, length: 15 meters.\material: Q235B, Q345B, 20#, 16Mn, and alloy material. 2. Rectangular Steel Tubes Min size: 30*40mm ... 6-40mm, Length: 15 meters.material: Q235B, Q345B, 20#, 16Mn, and alloy material.