The Knut Bø Muro-Style 100 B is a 4-inch (Ø100 mm) bathroom extract fan with an integrated backdraft damper and single-pole pull-cord switch. Rated free-air flow is 95 m³/h and the fan is intended for on-demand ventilation of bathrooms, toilets and utility rooms. It suits wall or ceiling mounting connected to standard 100 mm ducting.