REFILL – device sold separately. The Zevo Flying Insect Trap uses light to continuously attract flying insects (house flies, fruit flies and gnats) and capture them on to an adhesive backing that you never have to touch. No odors or messes! Use in any room in your home where flying insects are seen. Replace refill cartridge when it’s full of insects. Check it every 15 days or as needed. For best results, keep Zevo plugged in 24/7.