Kair Brown Gravity Grille 155mm External Dimension with 100mm - 4 inch Round Rear Spigot and Not-Return Shutters - Ducting Air Vent. This Kair Gravity Grille features a 100mm / 4 inch round spigot designed for air exhaust. It includes non-return shutter flaps that automatically close when not in use to prevent the backflow of unpleasant odors, noises, or drafts into your property. The 4 inch / 100mm male spigot on the rear of the grille is compatible with most pipes and hoses of a similar size, such as Kair 100mm Round Female Duct Pipe (DUCVKC250) or 102mm flexible hose (DUCP002/102/35). Installation is straightforward; simply push-fit the components together and seal if necessary using methods like mastic sealant, poly cement, or tape. It is ideally suited for outlets for bathrooms, toilets, or kitchen extractor fans, hydroponics, in-line extract fans, or cooker hoods. As a genuine Kair product, it is covered by the Kair 100% Satisfaction Guarantee. Manufactured in the UK, Kair products are known for their compatibility with an extensive range of fittings, outlets, and grilles in various sizes, offering a comprehensive ventilation solution. This item can be integrated into long ductwork runs for diverse applications including whole-house ventilation, passive stack ventilation, positive input ventilation, air conditioning, HVAC, and Heat Recovery systems. Kair SYS-100 plastic rigid ducting is suitable for both DIY and trade use, offering superior airflow performance and durability compared to flexible ducting. This grille is also available in Beige and Red. Specifications: 155mm x 155mm external dimension, 4 inch / 100mm round male rear spigot, gravity flap (no springs), compatible with Part F Building Regulations, independently tested airflow performance. Free Air: 7200mm2. Static Pressure Drop: 15 l/s = 10.94 Pa, 30 l/s = 18.59 Pa, 60 l/s = 24.21 Pa. Weight: 0.18 pounds.