Rectangular tubes are highly resistant to bending, allowing better use of the material, with a yield stress Fy = 3515 Kgf / cm ² and Fb = 0; 72 x Fy. Also they are very efficient in axial compression and are recommended as beams, for big moments, axial loads and moderate values ??(KL) small. Specifications and Properties of Structural Tubes BS – 6363 BS Structural Tubes – 6363 square section. With a yield stress Fy = 3670 Kgf / cm ², the structural tube BS – 6363 square section, presents values ??of inertia and turning radius that can withstand moderate axial loads.