EASY TO USE: Simply swing the Serving Sock like a racquet and avoid hitting your back; SIZE: Same length as a tennis racquet from grip to center of strings; IMPROVE: The Serving Sock helps your serve in various ways: rhythm and fluidity and by correcting awkward serving motions; FITS ALL: The Serving Sock can be used by beginners and experienced players. Try tossing a ball and hitting it with the sock as an advanced drill