"Bulb shape: ED-17. 20,000-hour average rated life. 150 watts. Brightness: 15,800 lumens. Bulb base: medium (E26). Size: 5-1/2""L x 2-1/8"" diameter. Lights exterior and large interior spaces efficiently at an economical price. NOTE: high-pressure sodium ballast (ANSI Code S55) required for operation. 2 bulbs per pack. For more on clean u...