These high quality stereos are perfect for high school, college or professionals. Zoom magnification ratio is 1x - 4x. Standard features include: Slip Clutch System, parfocalled and par-centric optical system and dual eye diopter correction. DIN Widefield eyepieces provide for maxium field of view. Incident (top) illumination has a dimmer switch for light variation & can be angled, (6V, 10W Halogen), the transmitted (bottom) light is Ultra Lite® 5W, 4100K Fluorescent "Cool Light". In-base (bottom) 5W, 4100K Ultra Lite® Fluorescent illumination provides economical "Cool" light even after all-day use (bulbs last 100X longer than traditional bulbs) Trinocular Body available. Comes with limited lifetime warranty.