Music nomad The Humitar
An acoustic guitar needs humidity to be stable and sound its best. A guitar that's too dry can crack or warp.
For this reason, Music Nomad designed the Humitar. Very easy to install in the soundhole, the Humitar maintains an ideal humidity level thanks to a sponge that retains more than 10 times its weight in water.
This means it releases its water longer than any other guitar humidifier. To see if you need to re-wet the sponge, simply open the hatch and squeeze the sponge with your finger.
If it's dry, rehydrate it with demineralized water if possible.
Ref. Euroguitar : 116357