Metal stress balls, also called Baoding balls or Chinese health balls, are used to improve dexterity, aid in meditation and improve brain function when carefully rotated in the palm of the hand. When knocked together, a gentle ring is heard. Set includes two balls in a matching, covered box. Product Dimensions: H4.5cm x W4.5cm x D4.5cm Packaged Dimensions: H5cm x W10cm x D5.5cm