4-pieces Bulb Shape/Size: T6, 0.6 inch diameter. Wattage: 30W. Bulb Length: 36 inch. Replacement for : T8 fluorescent bulbs Fits all standard T-8, T-10, and T-12 fixtures with ELECTRONIC BALLAST ONLY. ***Please verify your ballast before purchasing.*** Up to 30% brighter than standard T-8, T-10, and T-12 bulbs. This is a universal replacement bulb for T8 fluorescent bulbs. Manufactured from high-quality glass and environmentally safe solid mercury. T6 bulb is smaller in diameter than T8 bulbs, but it has great color rendition and it is brighter than most T8 bulbs. ***Please note: You may hear the mercury ball rolling in the light tube when you first handle it. This is environmenally safe solid mercury rolling in the light tube. It is safe and ready to use.*** Helios 11,000k Daylight standard high-quality versatile T-6 lamp which can be a universal replacement lamp for industry standard T-8 light fixtures. 11,000k lamps will emit warm full color spectrum light that creates a vibrant aquatic environment. This bulb has nanometer peaks in the blue, yellow and red color spectrums creating one of the brightest daylight bulbs available. For use: Saltwater, Reef, Planted, Freshwater aquariums, greenhouses, general office lighting and hydroponics. *Package includes: 4-pieces T6 Light Bulbs of 30W 36 inch.*