This tuning fork produces 2 different vibrations: Vibration C64 Hz with dampers (as marked on steamers). Vibration C128 Hz without the dampers The two dampers must be flush with the lower edge of the value markings of the two forks. The imprint "C64" on the dampers and the imprint "C128" on the tuning fork must all point to the user when the dampers are mounted. How to use: 1. Ask the person to close their eyes 2. The person's foot is placed on a flat or placed flat on a chair, striking the tuning fork 3. Place the tuning fork end on the joint of the person's big toe nail and place our finger under the person's big toe while feeling the vibration. 4. Ask the person's to tell when the vibration is not felt and read the scale on the tuning fork. 5. If the scale is equal 5, the person's vibration is normal. 6. If the scale is Less than 5, the person's vibration is abnormal. size:Length about 26cm Material:Aluminum alloy colour:Silver Package Contents: 1 x Tunning Fork Only the above package content, other products are not included. Note: Light 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.