This Kair Gravity Grille is designed for efficient air ventilation, suitable for both indoor and outdoor use. It features a 155mm x 155mm external dimension and a 5-inch (125mm) round male rear spigot that fits most comparable size pipes and hoses. The grille is equipped with non-return shutter flaps that automatically close when not in use, preventing the backflow of unpleasant odours, noises, or draughts. Its gravity-operated flaps do not require springs, ensuring durability. The installation is straightforward with a simple push-fit design, though sealing with mastic, poly cement, or tape is recommended for optimal performance. This vent is ideal as an outlet for bathroom or kitchen extractor fans, hydroponics fans, or in-line extract fans. It can be integrated into longer ductwork runs for various applications, including whole-house ventilation, passive ventilation, positive input systems, air conditioning, HVAC, and heat recovery systems, and complies with Part F Building Regulations. Airflow performance has been independently tested. Key Specifications: - Spigot Size: 5 inch / 125mm round male - External Dimensions: 155mm x 155mm - Material: Plastic - Colour: White - Features: Non-return shutter flaps, gravity operated - Compliance: Part F Building Regulations - Tested Airflow Performance: Free Air: 11,600mm2; Static Pressure Drop at 15 l/s = 6.43 Pa, 30 l/s = 9.91 Pa, 60 l/s = 11.25 Pa. - Weight: 0.18 Pounds - Manufacturer: Kair