Square section heavy duty aluminium truss twist-resistant version with 40 cm long sides and lenght 300 cm; it is characterized by the introduction of Ø 48 x 3 mm chords and Ø 20 x 2 mm diagonals on all the faces. This truss constitutes Varitower 3-40. It replaces the old Heavy Duty series QD40S and QD40SA.