There is a difference in black light (UV) lamps. Insect-O-Cutor's lamps are pre-tested for high output. Off-the-shelf black lamps can vary by as much as 40% in the UVrange needed to attract insects. They aren't considered defective for other purposes, but you should avoid using them in your bug killer. Starting with a high output lamp is always worth the effort, because all UV lamps lose effectiveness long before they burn out. In fact, useful life for attracting insects is about 9 months. Many of our customers relamp every spring, prior to the heavy insect season. For this reason, each lamp is conveniently labeled with a date. Use in all brands of electrocutors. For best results, choose one filtered and one unfiltered bulb for units that use two bulbs.