Diffusers are air terminal devices of that are directly attached to a round ventilation duct. A diffuser is used for supply or exhaust room ventilation, and uses a centrally located rotating disc for air flow control. The Awenta air diffusers can be used in ceilings as well as in walls. They come as supply, exhaust or supply/exhaust types, are made of plastic or stainless steel for duct sizes from 80 to 200 mm, and can be installed in a variety of rooms.