Measuring less then 1.3 mm (.055") in diameter these Replacement Bulbs are truly a tribute to the bulb maker's art. Perfect for small scale applications where a flashlight battery or 1.5V power source such as the CK1009G transformer is available. They may also be used individually with a 12-volt transformer if connected in series through a CK1100, 680 ohm dropping resistor. Draws less than 15 ma at 1.5 volts. 1,000 hour bulb life.