PTI-IS Metal Inline Booster Fans are engineered to boost air in forced air heating and cooling systems without upsetting the balance in the closed-loop system. Each fan body is made of steel construction with powder coated baked paint and is suitable for various environments including gas work shops, indoor growing rooms, warehouses, etc. The motor features a permanently lubricated bearing that operates quietly and requires no maintenance. The fans are fluted on both ends to be easily mounted in-line with the existing duct work to increase airflow. Diameter: 4inch / 6inch / 8inch.