Zero In® UV Light Kitchen Insect Killer Refills provide effective, poison-free control of flies and other flying insects in the kitchen. Especially effective and safe in food preparation areas and for living and dining areas where flies may be a nuisance and health risk. Use refills in the Zero In® UV Light Kitchen Insect Killer for best results. The ultra violet LED lights are highly attractive and will enhance the effectiveness of the yellow sticky traps. Each refill is designed to last 21 days or even longer. Very heavy infestations may require more frequent replacement if the trap becomes full of dead flies.