ECLIPSE FANS are compact, ultra quiet, easily installed & have a 10 year limited warranty. Quiet, powerful, high capacity, & compact. They are rated for continuous operation in humid environments & are designed for high static pressure applications including: carbon filters & long complicated runs. Fan speed may be infinitely varied with optional speed controls. They come with a factory installed grounded cord & robust mounting brackets. The sizes correspond to the diameter of the ducting that will be needed.