The S355JR (E355B) square steel pipe is a high-strength structural tube made from low-alloy, high-tensile steel. It is widely used in construction, machinery, transportation, and mechanical structures where durability, load-bearing capacity, and reliability are essential.

The S355J0 (E355C) square steel pipe is a high-performance structural steel tube designed for applications requiring superior strength, excellent toughness, and reliable weldability. It is part of the EN 10025 and EN 10210 series of European structural steels, commonly used in construction, mechanical engineering, transportation equipment, and general manufacturing.