RS Series inline tube fans are designed to fit standard-sized spiral duct, including 4-, 5-, 6-, 8-, 10-, and 12-inch sizes. The fans feature 10 different models, providing a performance range from 176 CFM to 970 CFM. They feature external rotor motors with integral impellers. The fans are designed to allow for 100% speed control, even with inexpensive electronic controllers, thus allowing for matching the airflow to the system design while promoting energy conservation, the company states. Accessories available include mounting brackets, back-draft dampers, protection guards, fast clamps for rigid ducting, and flexible couplings.