Lasko 20"Commercial Metal Box Fan with All METAL Constructive and Non-Corrosive Aluminum Blades, 3 Powerful Speeds & Patented Safety Fuse Included 20-Inch Box Commercial Metal Fan with Non Corrosive Aluminum Blades Top-Mounted Control Knob with 3 Powerful Speeds All Metal Structure - Body, Blade, Handle with Safe Rounded Corners Enclosed Motor for Safe Window Use, 3-Prong Grounded Plug with Patented Safety Fuse E.T.L. Safety Listing, Meets OSHA Requirements