Lily's Home Solar Radiometer Crookes Light Mill for Detecting Sunlight and Electromagnetic Radiation, Fascinating and Functional Gift Ideal for Student or Science Guru, Clear Sphere (4" Diameter, 9" T Magnificent Glass Radiometer, makes a great gift for the one who have everything. All made of glass. Globe is 4 inch in diameter and stands 9 inch tall. This physical and technical miracle shows you in a clear way how sunlight is converted to energy Place near a window or under incandescent light and watch as the vanes rotate Lily's Home is a registered trademark of Solar Wholesale, LLC.