The Flowtron Replacement UV Bulb is your friend during a crisis. The UV Bulb is essentially the heart of the Bug Zapper as it is the main method of attracting mosquitoes and other insects. In case you need to replace your UV bulb, this replacement UV bulb will be there to save the day (and night) for you and your family. This is a 3-Pack, which is cheaper than buying three separate bulbs. The Flowtron BF-35 Replacement UV Bulb is compatible with Flowtron BK-15 Outdoor Bug Zapper. The Flowtron Replacement UV Bulb is the main force of attraction for the insects. When the insects come near the bulb, the insects get zapped and are killed instantly by the nearby non-clogging, high-efficiency shock grid. The UV Bulb enables the Flowtron Bug Zapper series of products to work continuously to ensure you and your family are safe at all times.