4'' Grow1 Booster In-Line Duct Fan

4" Booster In-Line Duct Fan. Duct booster fans increase airflow in hard-to-ventilate rooms. They are durable quiet easy to install and fit into metal or flex ducts. Their strong motors excellent performance and higher temperature ratings set these booster fans apart. Rated for both heated and cooled air and perfect for outdoor AND indoor use.