Reducer disc gives five different free area settings between 33 and 100cm² (5 to 15.1/2 in²). Tube diameter: 125mm. Through wall length: 300mm to 340mm telescopic. For high rise applications when installation from inside the building is required. External colour: Terracotta/internal vent white. for appliances up to 27 kW Net - (30 kW Gross).