Dunlop Pro Double Yellow Dot Squash Ball The official ball of Squash Australia, World Squash Federation (WSF), Professional Squash Association (PSA), and Women's International Squash Players Association (WISPA) and the only ball used in all international professional competition. An elastic hydrocarbon polymer is impregnated with 12 compounds resulting in a construction material with unrivalled playability and durability characteristics. The ultimate performance squash ball for professional, tournament and club players.