This mosquito repellent refill from ThermaCELL includes 3 repellent mats that each last up to 4 hours, plus one butane cartridge, providing a total of 12 hours of protection against mosquitoes, bugs, and other flying insects. Mosquito repellent mats should be replaced after four hours of use to maintain the power and performance of eliminating biting insects. The refill in the package fits all ThermaCELL mosquito repellent lanterns and appliances.