Soler & Palau DA 18"/450MM Tubular Duct Direct Drive Axial Fan S&P Compact Wall/Duct Axial Fans feature, as the name suggests, an extremely compact design created by the combination of an external rotor motor matched with a direct drive wrapped around an impeller hub. This very low profile design optimizes airflow performance while minimizing noise generation. Both wall and duct mounted versions require an absolute minimum depth for any given wall, ceiling, panel or in-line duct mounted installation. All models include asynchronous induction capacitor run and start motors. Wheel / Impeller Manufactured from glass filled UV resistant polyamide. All models have been independently safety tested by Underwriters Laboratories, Inc and are UL and cUL Listed.