Transitions are used when a duct system of one cross-section is transferred to a duct system of another cross-section. Transition can be carried out both from round to round, and from round to rectangular cross-section of the duct. Note For D 100-315 A=40 mm, for D 355-800 A=60 mm, for D 900 and above A=100 mm. It is possible to produce transitions on special order of any design.