The STIGA Spin Tracker Tennis Balls multi-pack includes 6 white STIGA 2-star (40mm) ITTF regulation size and weight table tennis balls. Crafted from high quality ABS material, these table tennis balls help players track and monitor ball rotation and teaches how to generate and counter spin. Their seamless, perfectly round design means these superior table tennis balls offer consistent bounce and spin and are long lasting. This multi-pack is perfect for practice and training.