Soundhole humidifier with convenient user-adjustable hygrometer Fits easily in the soundhole of your steel-string acoustic guitar Humidifier releases moisture evenly and slowly Hygrometer takes all the guesswork out of adjusting humidity levels Drip-resistant polyvinyl acetate sponge holds 10 times its dry weight in water and maintains humidity for 15 days or more before needing to be recharged Features 4 openings for water vapor to escape, with 4 additional openings that can be punched out for more humidity in dry climates Sponge is easily recharged by moistening it with distilled water