An easy to use, no mess, low maintenance case humidifier, the Humitar features a holster with a strong adhesive backing that can be placed in any open area inside your case. Works great for acoustic and electric guitars, mandolins, cellos, and other large case instruments. Is it time to check the Humitar? Pop the top and touch the insert; if it's wet leave it, if it's dry, it's time to rehydrate.