Housing is UV treated polyethylene, sturdy and corrosion free. Slanted design projects 12" from outside of barn. Condensation flows down and away from barn, keeping walls clean and dry. Inside mounting is flush, eliminating obstructions along walkways. Aerodynamic housing funnel encourages free air flow. 12" - 24" Units have variable speed with energy efficient direct drive. All motors are epoxy coasted, feature totally enclosed air-over design, thermal overload protection, and double-sealed, permanently-lubricated ball bearings. All fans carry a one year conditional guarantee. CSA approved.