The 40 lumen, 4.5V (volt) to 6V LED (light emitting diode) replacement bulb is the ideal way to upgrade old flashlights. This conversion bulb operates with any 3 cell, 4 cell, or 6V lantern or flashlight. This bulb is a 10 year bulb and allows for 100,000 hours of use before any change is required. The 40 lumens of light output provides greater value and visibility to older flashlights.