40 hour refill, for use in the Thermacell radius zone Mosquito repellent only. When used with Thermacell radius repellent, this refill will provide up to 40 hours of Mosquito protection for you and those around you. The easy-to-use radius repellent offers a better alternative to topical Mosquito Repellents. That’s because radius treats the area around you, rather than your skin. That means no messy sprays or oily lotions. The scent-free radius repellent is rechargeable, compact, and powerful. Radius uses heat to release a proven repellent, creating a zone of Mosquito protection for you and those around you. Powered by a lithium-ion battery (rather than butane), radius is air travel friendly and consistently operates at any elevation. Operates with a single refill component; liquid refill cartridges available in 12 and 40 hour sizes. For best results, use on days with light or no wind (bugs are at their worst on these days), and allow 5 minutes to form a complete zone of protection around the unit. Thermacell radius is safe, effective, and comes with a 100% satisfaction guarantee. With Thermacell, turn it on. Mosquitoes GONE.