Easy to operate Feature:Keep your reference tension in check with the tension calibrator stringer tools A must have for proper stringing machine maintenance. A racket that has just been put on or used for a period of time, usually the midpoint value of value measured by the pressure gauge is too small, and the pressure value around to be more pounds, compared to the horizontal line, vertical 's beat value to be more pounds. Therefore, we usually use the measurement of four weeks (vertical line at 2/4/8/10 o'clock) to understand value of the racket. How to use: In the first step, rotate the disc counterclockwise to zero the scale; In the second step, the two small cylinders of the pressure measuring device are perpendicular to the of the racking and inserted in the direction; In the third step, turn the pressure gauge clockwise. When the vertical line is placed in the of the manometer, it is enough to find the scale value of the corresponding dial. Note that value is not exactly the same as the pound value, but some points tend to be pounds. colour:black Material:PVC Package Contents: 2 x Tension Calibrator. 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.