The OH-1 guitar humidifier is a soundhole humidifier designed to maintain 45-55% relative humidity inside the guitar body when the humidity outside the case is between 25-40%, provided that the guitar is already hydrated. The OH-1 is not designed to restore humidity to a dried out guitar. The OH-1 is our most popular model. Each Oasis® OH-1 comes with a stabilizer bar for mounting the humidifier and a 10 cc. syringe for distilled water filling control.