Features: The box hygrometer contains a mechanical movement that does not require battery replacement, making it very easy to use. Easy Installation: 37mm in diameter, the hygrometer disk-shaped and easy to install in different storage containers. Bells-shaped, with pointers scale. Designs: Made of high quality alloy material, beautiful silver frame, fashion and simple, durable, not easy to break, very stable pointers, can be used for a long-time. Wide Application: can be used in a variety of environments, case, piano case, guitar case, file cabinet, greenhouse nursery, factory and so on. Specifications: Material:Metal Type:Hygrometer,Thermometer(optional) Frame Color:Silver,Gold (optional) Diameter:27mm/1.06'',37mm/1.47'' (optional) Temperature Test Range: -30~60℃/-20~140°F Humidity Test Range: 0~100RH Package Includes: 1Set Hygrometer or 1Set Thermometer note: Please allow 1mm errors due to manual measurement. Due to the difference between different monitors, the picture may not reflect the actual color of the item.