The SKLZ Impact Softballs are heavy duty plastic balls that gives players the feel of where contact is made. Constructed with proprietary pop-back material similar to the material used to make car bumpers, Impact Softballs keep their shape and won't crack like standard practice balls, even after thousands of swings. Built to provide instant feedback on contact, they help hitters tune their swings to find that all-important sweet spot. Larger ball size mimics standard softballs.