Grover humidifier kit for most acoustic guitars. Maintains a proper moisture level if your guitar is stored in an area prone to dryness. 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. Made of soft latex which is harmless to all instrument finishes. Includes a cover to seal the sound hole during use. Easy-to-follow instructions and a user-friendly humidity gauge are included.