These grilles are used in round ducts for air supply and extraction. As an option single or double row blades types can be manufactured. The grilles can be manufactured in any desired radii to enable easy assembly into the ducts. Moving blades enable the throw direction of the air to be adjusted either vertically or horizontally. An optional damper can be attached for regulation. Round blade grille frames and blades are made from aluminium and only 1st class aluminium profiles are used.