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. Humidifier for violin Is inserted into the sound hole of the instrument. Protects instrument from damages due to dryness. Includes 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.