The Thermacell Mosquito Repellent refill pack includes 4 bottles designed to provide 36 hours of protection from mosquitoes. These liquid refills are odorless and suitable for use both indoors and outdoors. With an EPA registration number of 71910-11, Thermacell ensures effective mosquito control with a repellent/deter method that does not harm the environment. The battery-operated power source makes it convenient for camping, hiking, and other outdoor activities. Made of durable plastic, this product is ideal for those looking to enjoy the outdoors without the nuisance of pesky mosquitoes.