1Built-in AD584kh, highest accuracy and stability 2The MCU switch 4-channel reference voltage output with LED indicators 3Single-button operation switch reference voltage 4 Easy to carry, can be charge by DC 5V,with charge indicator 5Transparent case can protect module from damage and provide clear view Features: Built-in AD584kh, highest accuracy and stability. The MCU switch 4-channel reference voltage output with LED indicators. Single-button operation switch reference voltage. Easy to carry, can be charge by DC 5V, with charge indicator. Transparent case can protect module from damage and provide clear view. Specifications: Reference Voltage: 2.5V, 7.5V, 5V, 10V Banana Socket Output: 4mm Weight: 92g(approx.) Package Includes: 1 x Voltage Reference Module Note: 1, Please check input battery charging voltage and do not charge with more than 5.5 volts DC. Please charge with a USB adapter. 2, Battery is NOT included.