This is a ThermaCELL Mosquito Repellent One Refill. One refill includes 3 mats and 1 cartridge, for a total of 12 hours of repellency. To continue to repel mosquitoes repellent mats should be replaced after 4 hours of use. Butane cartridges last up to 12 hours each. Refills fit all ThermaCELL mosquito repellent models.