The PU stress ball is made with high-quality PU foam (polyurethane), and they are hypoallergenic and nontoxic, can be applied for a long time, with good elasticity that comfortable to hold and touch, gives you pleasant playing experience.Each ball is about 2.5" in diameter.It features a resilient construction that returns to its original shape after each squeeze, providing long-lasting performance.This stress ball relief is useful for those with ADD/ADHD, OCD, autism, or high anxiety levels. They are also ideal options for you to relieve your stress, anxiety or anger, making you to spend a peace and relaxing time. We can make other size that you need.