Centrigual in-line duct model works as an internal air mover and is a quiet, forward-curved, ball bearing, double inlet blower. Access panel allows convenient motor and drive installation and servicing from either side. 1/2" internal fiberglass insulation helps isolate noise and overcome condensation on cabinet when used in cooling applications. Use indoors with clean-air heating, cooling, and ventilating systems. Up to 25% blower speed and cfm reduction using variable pitch motor sheaves when ordered with motor and drives.