DESC: As thousands of repeat customers will tell you, ThermaCELL is unbeatable at repelling mosquitoes, black flies, and no-see-ums. Tests by the US Army have found ThermaCELL to be up to 98% effective against mosquitoes, black flies, and no-see-ums within a 15x15 ft area.ThermaCELL Refills work with all ThermaCELL productsThe Single-Pack Refill comes with one butane cartridge and three repellent mats, providing up to 12 hours of protection. Refills are also available in a value-pack which comes with four sets of refills (four butane cartridges, 12 mats for up to 48 hours of protection).This product is registered by the EPA.