1. It employs precise optical structure, of light is very clear and precise measurement. The measurement results are displayed digitally, and the left eye and right eye measuring values are displayed separately. 2. Simple and rapid measuring operation, and free operation of the direct PD adjustment lever are possible. 3. When the measuring operation is finished, the auto power off and memory function, enable to save the power and not to lose the data. 4. It can also be used in monocular the left eye and right eye separately. Electric Voltage: (without includ) Power: 5W Colour:White Material:plastic Package Contents: 1 x Digital interpupillary distance ruler 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.