The Thermacell Mosquito Repellent unit is just what you need to keep mosquitoes and other annoying insects away while hunting. The unit works by heating a mat saturated with mosquito repellent. It can create up to a 15' x 15' mosquito free zone, and it is also odor free and EPA approved. The Thermacell will also repel black flies, no-see-ums and sand flies. Included with the unit are 3 repellent mats and 1 butane cartridge (extras can be purchased separately). The holster allows you to transport your Thermacell Mosquito Repellent device hands free. It features storage space for butane cartridges and repellent mats (not included), and it can be attached to a belt, backpack or even a tree stand. The design of the holster also allows butane cartridges or repellent mats to be changed without removing the device.