Medium-bases screw-in fluorescent. Light output equivalent to 25 watt incandescent bulb. 5.25 inch overall height. 10,000 hour life. •Same light output as a 25 watt incandescent for only 9 watts. •Very narrow ballast fits into almost any existing fixture. •Instant-on, no lamp flicker. •10,000 rated life is over 10 X longer than standard inc. bulbs. •430 Lumens light output.