Dimensions of rectangular bends are in accordance with types described in rectangular ducts.
Bends are characterized by application of radius as well for inside wall as for outside wall
of an installation while in bends external parts are made of two straight sections connected at 90° angle.
In the case of greater dimensions - more than 400 mm - guide parts are applied to enable a more uniform flow of air.
The number of guide parts depends on a width of a duct and amounts to 1, 2 or 3.