The Xelerator is a great tool for warm up as well as building arm speed. It is a self-correcting apparatus that helps develop a perfect pitching plane. As a pitcher does continuous circles, the weight of the Xelerator will lengthen the arm throughout the circle. If the arm circle is on the correct plane, the Xelerator will fly smoothly through the air. Muscle memory of the perfect plane translates into increased pitching speed and accuracy. Incorrect shoulder, elbow or wrist movements will make the Xelerator wobble. Therefore, its great for creating muscle memory to correct ugly arm circles!!