This Thermacell refill pack includes 12 repellent mats, providing a total of 48 hours of mosquito protection. These mats are designed for use with the Thermacell Backpacker Mosquito Repeller and offer a mess-free, scent-free, and DEET-free solution. The active ingredient, Allethrin, is a synthetic version of a natural repellent found in chrysanthemum flowers. Each mat provides 4 hours of protection, effectively repelling mosquitoes, black flies, and other flying, biting insects without any flame. They are silent and virtually odor-free.