This listing is for a combination pack of the Thermacell Mosquito Repellent with the Earth Scent Refills. The Thermacell Mosquito Repeller Device is a safe, simple way to create a large area free of annoying mosquitoes, black flies and no-see-ums. This pocket-sized unit is powered by a butane cartridge and refillable mats. After a quick five-minute warm-up, the unit provides hours of protection to a 15 by 15 foot zone against pests. Approved by the EPA and used by the U.S. Department of Defense, Thermacell has proven to be a game-changer in area mosquito repellent.