Yel-O-Jaket – “Sting the Ball”, Our Yel-O-Jaket product will help you do exactly that. Sting the ball! Say goodbye to weighted bats and and awkward swing aids. The Yel-O-Jaket is all youll need for pre game warm ups and practice. Just a few minutes of swinging the Yel-O-Jaket a day will improve your bat speed, and earn you a consistent bat path. Using the Yel-O-Jaket will keep your upper body flexible and help prevent injuries and make you a better batter all around. The YOJ is perfect for kids and adults of all expertise.