Dampit

The importance of proper humidity levels for strings and woodwind instruments is difficult to overestimate. Drying out of the wood significantly affects the sound quality and appearance, and can lead to cracking of the instrument body.
One of the most effective and simple solutions to this question came from the inventor and professional musician Ralph Hollander. The original humidifier for stringed instruments, Dampit has been protecting wooden instruments for over 40 years. Invented and patented in 1966, it moisturizes the instruments of thousands of musicians around the world.
Using Dampit is very simple: immerse the humidifier in water for 20 seconds, gently wipe the outer tube dry, place inside the instrument. Once the Dampit is almost dry, repeat the process above.
An indicator is supplied with each humidifier to show the level of humidity in the room and to help determine how much you need to use Dampit with your instrument.
Another important advantage of Dampit is its size. It is so small and light that it has absolutely no effect on the sound, which means you may not get it out of the instrument while playing.