99-101mm sound hole diameter. Used as a guitar humidifier, simply moisten the included sponge and install for reusable humidification. Working as a guitar dehumidifier, using the included desiccant to absorb around your guitar. Can also be used as a normal sound hole cover to eliminate unwanted feedback. Soft rubber covers the insert edge, no damage to your guitar. Specifications: Material: Plastic + Rubber Compatible Sound Hole Size: Dia 99-101mm Item Size: 11 * 1cm / 4.3 * 0.4oz Item Weight: 53g / 1.9oz Package Size: 14 * 12 * 3cm / 5.5 * 4.7 * 1.2in Package Weight: 102g / 3.6oz Note: This sound hole cover is not suitable for guitars whose fretboard has reached the sound hole. The guitar showed in the picture is not included. Package List: 1 * Sound Hole Cover 1 * Sponge 1 * Bag of Desiccant