Features: Designed for acoustic guitar with 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 moisture around your guitar. Can also be used as a normal sound hole cover to eliminate unwanted feedback. Soft rubber covers the insert edge, and no damage to your guitar. Specifications: : ABS+Rubber Color: As The Picture Shows Package Weight: approx.60g Size: approx.11x1.2x11cm/4.33x0.47x4.33in (More Size Detail, Please See Photo.) Note: Please allow 1-2cm error due to manual measurement. Please make sure you do not mind before you bid. Due to the differences between different monitors, the picture may not reflect the actual color of the item. Thanks! Package includes: 1Pc x Guitar Sound Hole Cover Humidifier