Features: 1. The same port can output reference voltage: 2.5V, 7.5V, 5V, 10V. 4mm socket output interface. 2. Compact and portable: being so mini and light-weight, this product does not take much space and can be easily taken away. 3. material: This product is made of high quality material, and long service life. 4. Built-in AD584, highest accuracy and stability. The MCU switch 4-way reference output voltage with LED indicators. : Power supply: 3.7v Li-polymer battery (not included) Material: PC+Metal colour: As Shown Package Contents: 1 x Voltage Reference Module Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.