The material used is fiberglass reinforced nylon-the fibers are mixed into the nylon plastic-its a specialized molding process. The fibers are indeed-glass.Special equipment is required to mold the material.Traditional rotating screw plasticizers and injection molders can't be used becuase they would tear or shred the glass fibers.Milwaukee power tools and some other power tool companies use the glass nylon in power tool housings.Vortech uses it in their vacuum cleaner housings.Its tough,but I would rather use metal for the fan.