The dunlop pro squash balls are designed with professional tournament and club players in mind these performance double yellow dot balls incorporate the n 1sr molecular technology which provides excellent playability and makes them more durable the dunlop pro are the official balls of the wsf world squash federation psa professional squash association and wsa womens squash association they come in a standard size of 40mm and are supplied as a 6 dozen pack 6 x 12 ball box