This is a brand-new 13 watt high output circular fluorescent bulb that fits many gooseneck magnifying lamps, table lamps, and magnifier lights.  It will produce 13 watts only in fixtures whose power supply is designed for this output level.  

The T4 designation means the tube is 1/2 inch in diameter.  The outside diameter is 4.75 inches. The connector for the bulb has four brass pins arranged in a square, facing outside the bulb. If your lamp has pins facing inside, you will be able to use this bulb only if the connector wire is long enough to wrap around the bulb and the head has enough room for the outside connector.

The 6400 degree color temperature means the lamp gives bright balanced daylight illumination.

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