Invented by Cheri Kempf, the Baseball Spinner is a training aid designed to teach the spins and rotation directions of the baseball. Endorsed by pitching guru's Ernie Parker and Mona Stevens among others, the Baseball Spinner is a great pitching aid whether you are working on the basics of releasing the baseball or the advanced spins of the rise, curve, or drop. Used at many of the top collegiate programs throughout the country, the Baseball Spinner provides instant feedback to pitchers, catchers, and coaches. Although the Baseball Spinner was originally designed for pitchers, many coaches use it to teach correct fundamentals of overhand throwing as well. An Instructional Booklet is included in the package.