The thermacell cartridge refill effectively repels mosquitoes by creating a 15 ft zone of protection when used with thermacell devices and thermacell repellent mats. use this fuel-only refill for when you have spare thermacell repellent mats.Specifications and Features: Contains 4 refill fuel cartridges lasting up to 12 hours each 48 hours of mosquito protection; spray and mess free; DEET-free Compact, lightweight and portable for 15 ft protection zone