I have a few striped balls in my pitching bag for use when teaching the roll drop and the riseball. They are invaluable. I place a stripe right down the middle of the ball and use them in close rotational work to insure the proper rotation is being imparted to the ball. The stripe gives instant feedback to the player and is easy for the catcher to see and determine what rotation has been imparted to the ball. When throwing a riseball or a peel drop (straight dropball) the pitcher and catcher should see a solid line as the ball flies toward the target. If the line looks solid, the rotation is probably correct. If the line wavers or is non-existant, the rotation is incorrect and more rotational work is needed. The straight drop (peel drop) is released off the "birdie" finger and the rotation is clockwise as viewed from 3rd base. If any other rotation is being imparted to the ball, the ball will not drop. The riseball is just the opposite from the peel drop. The ball must have counter-clockwise rotation as viewed from 3rd base.
Try utilizing the striped ball in your next practice and watch the throwing errors disappear!