ThermoFlo Elbow is a radius forming brace for flexible ducts that's engineered to improve the airflow and efficiency of your grow room ventilation system. It saves energy by eliminating kinks and airflow restrictions and shapes flexible ducts into efficient 90-degree elbows. By improving airflow, ThermoFlo Elbow also makes it easier to provide the ideal environmental conditions for your plants, and ensures you get the best results from your grow every time. Made from 100% recycled materials, it works with all kinds of flexible ducting and is U.L. approved. ThermoFlo Elbow is perfect for any indoor gardening operation and is easy to use. Install on new ducting, or use it to retrofit existing flexible ducts. (For best results use in combination with ThermoFlo 2000SR ducting.) One size fits all 4 in to 16 in flexible ducts. Easy to install, no special tools required.