Provides Instantaneous Feedback. Develops Proper Throwing Mechanics For All Types Of Pitches. Made With 100% Real Leather & Baseball Seams Increase Your Throwing Accuracy & Mechanics Guaranteed -- If The Ball Wobbles At All You're Not Throwing Correctly No Wobble = Proper Throwing Mechanics Which Will Also Increase Overall Velocity & Spin Rate. And Will Reduce Arm Stress And Injuries 5 Pitches With 1 Ball - 2 or 4 Seam FastBall, Change Up, Curveball, Split Finger - Maximize Your Throwing And Pitch Mechanics Easily Using The Insider Bat Baseball Spinner! Made in the USA The Insider Bat Baseball Spinner will help pitchers, catchers, and coaches to better understand the rotation of the ball and what is required to impart that rotation. The Insider Bat Baseball Spinner is the exact diameter and weight of a baseball. It is a valuable tool to ingrain the proper mechanics of overhand throwing in all players. It can be used exclusively by pitchers for learning proper rotation on a baseball, which is required for movement, All pitches can be thrown with the spinner including fastball, split finger fastball, curve, change, slider, sinker, and screwball.