Straight duct, stiffened with transverse trapezoid corrugations, which reduces the risk of noise generation. Larger dimensions have stiffening profiles and/or internal rods. Installation height of these profiles is 23 mm.
Ducts are normally supplied with a strong joining profile RJFP 20 or RJFP 30 at each end, but can also be supplied as a flexible piece, where the joining profile on one end is not fixed. Also available with an end cover fixed by joining profiles.