The DAddario Guitar Humidifier Pro is perfect for maintaining and protecting your guitar. The humidifier pro can humidify your guitar for longer periods of time before needing a re-fill. Prevents unwanted cracks warped necks and shrinkage and keep your guitar healthy and playable. Moisture is slowly and evenly released by the humidifier for the perfect level of humidification. You can check the sponges status simply using the humidifiers stopper. The specialised sponge can hold up to 12x its weight in water.