Humidifier for bigger instruments with larger bodies, such asdouble bass, but alsoacoustic basses in the shape of an acoustic guitar. Isinserted into the sound hole of the instrumentProtects instrument from damages due to drynessContains a humicator (humidity level indicator)Made of soft latex which is harmless to all instrument finishes, these humidifiers release moisture to maintain proper humidity levels. Easy-to-follow instructions and a user-friendly humidity gauge are included. It is essential to maintain a proper moisture level if your instrument is stored in an area prone to severe dryness and/or cold (such as a heated home). The Grover humidifier helps to prevent adverse effects such as bad string action, buzzing, protruding fret ends, cracking, top-sinking, and other damage caused as a result of dryness.