Three-color LED indicators change with temperature, letting you know the current temperature at a glance without a thermometer. Powered by a mini hydroelectric generator, there is no external power supply needed. It uses a safe 5V-2MA voltage with no leakage and is non-harmful to the body. Temperature-sensitive and color-changing. LEDs provide a long service life, rated for more than 50,000 hours of operation. All copper construction offers excellent anti-corrosion properties, high strength, and good resistance to deformation. Key attributes - Function: color-changing temperature indicator - Power: 5V-2MA, no external power supply required - Material: all copper - Longevity: >50,000 hours Applications - Indoor desk or shelf display to monitor room temperature at a glance - Outdoor camping gear or portable equipment with battery-free operation - Workshop or electronics station to monitor heat buildup in tools or components