"Bulb shape: ED-17. 20,000-hour average rated life. 100 watts. Brightness: 9,500 lumens. Bulb base: medium (E26). Size: 5-1/2""L x 2-1/8"" diameter. NOTE: High-pressure sodium ballast (ANSI Code S54) required for operation. 6 bulbs per pack. For more on clean up and safe disposal, visit epa.gov/cfl."