1. Feature:Keep your reference tension in check with the tension calibrator stringer tools2. A must have for proper stringing machine maintenance.3. 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.specification:1. 0-42lbs2. Know when it is time to restring3. Easy to operate4. Model:AC-SM200colour: blackMaterial: PVCPackage Contents:1 x Tension CalibratorOnly 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. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.