Tennis Dial Arm Strap Adjustable Training Wrist Band Tennis Swing Correct Exerciser

Correct wrong movement of wrist/upper arm hitting ball.;Quick to form correct swing muscle memory.;Improve stability of ball hitting.;Dial design to easily adjut and fits your upper arm/wrist well.;Easily attach to your tennis racket(not included).;Fits circumference from 11cm(4.3) to 37cm(14.6).