Taylor Hygro Thermometer Mini RH range: 10 to 99% (+/- 5%)Temperature range: 14 to 140 degrees FBuilt-in memory stores MAX/MIN readingsBuilt-in tilt stand and LR44 batteryLow battery indicator Dimensions: 2" x 1.5" x .63" (51mm x 38mm x 16mm)To maintain proper levels, you may need to use a guitar humidifier (sold separately)Note: 45-55% relative humidity is optimal for your guitar