Focus on the basics and improve your overall throwing technique with these four-seam throw trainers. The striped ball turns purple when thrown to give instant feedback on revolutions per minute. Ball will only turn purple when using proper throwing form to promote better arm angles. Color changing design makes practicing the perfect fast ball fun for youth athletes throw after throw. While the white ball features a black rotation guide and raised seams to provide guidance on grip and proper back spin. Consistent practice builds muscle memory to improve overall performance. After practicing with the throw trainer you’ll be ready to throw someone out at the plate, turn a double play, or step on the mound knowing you’ll throw a strike. Both balls are the same size and weight as a standard baseball.