This Thermacell Mosquito Repellent Refills contain 4 butane cartridges and 12 repellent mats. Each cartridge works for up to 12 hours to provide a total of 48 hours of repelling power. They will repel mosquitoes, black flies and no-see-ums so you can enjoy your outdoor activities. Repels mosquitoes, black flies and no-see-umsWorks with Thermacell mosquito repellent productsEach butane cartridge lasts for up to 12 hoursEach repellant mat lasts up to 4 hoursRefilled products can be switched off to be used at another timeExcellent for hunters