Make sure your ThermaCell protection from mosquitoes and other bothersome insects does not run out by keeping extra butane cartridges with you. The ThermaCell Butane Cartridge Refill 2 Pack helps you keep a safe backup supply of butane. Refills can be stored for long periods of time, including between uses. This two pack of cartridges provides up to 24 hours of energy for ThermaCELL appliances. Does not include repellent mats.