What impact does dryness have on guitars? Wood deformation, panel cracking, paint cracking, and changes in sound quality,GHD-04 guitar sound hole adjustable humidifier, integrating humidification, anti whistling, and guitar protection. No matter where you are, the compact design is convenient to carry around. It uses quality silicone material to fully wrap the humidifier body, ensuring stability, and no damage to the guitar. Adjustable humidity: By using the humidity control switch on the panel, you can easily adjust the humidity level of the guitar.The unique breathable holes and sponge of the humidifier can prevent moisture leakage in the guitar. Real time humidity meter: intuitively displays the humidity inside the guitar and the surrounding environment, making it easy to accurately control Preventing whistling: Closely fitting the guitar sound hole, effectively eliminating sound feedback and avoiding whistling during performance The size of the sound hole ranges from 100mm to 110mm. Colour:Black Material:plastic Package Contents: 1 x guitar humidifiers Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.