These Sensory Discovery Balls from Haba are 4.5cm in diameter and each has a different effect contained within. Carefully made of wood and designed to trigger the curiosity of any child. Wonderfully tactile, they are great to play with. Whether rolling them across the room or exploring the different sounds they make, they will appeal to babies. A lovely set of visually stimulating toys. Pop them in a bag and jingle or use them in guessing games. This set of 4 includes a ball with a peep hole, rattle and foil mirror and also a squeak.