SKLZ Thunder Bolt Training Balls (Pack of 6), 8-Inch Lightweight foam practice balls Made to work with the thunder bolt pitching machine Soft, durable and safe for players of all ages Comes as pack of 6 8 inch circumference and weigh 2 oz Designed for the Thunder Bolt pitching machine and everyday training Small size encourages more focused batting training 8.25" circumference, 2 oz. ball provides a baseball hitting experience Limited ball flight perfect for backyard practice Soft, durable and safe for players of all ages