The Oasis OH-14 Case Plus+ humidifier was designed for use in especially dry climates -- deserts, mountains, and the frigid north. Keep your guitar and other stringed instruments free from environment-related cracks with this in-case humidifier. Held in place with neodymium magnets, the OH-14 Case Plus+ provides up to 50% more daily humidity than the OH-1 guitar humidifier and the OH-6 case humidifier.