Choose a 4 ball EPCO set if you would like to have another color option (e.g. buy a 4 ball white set to supplement your red and green sets) or if you need to replace more than 2 balls in your set or if you want a cheaper option than purchasing a whole set - Green balls come in 4 sizes - 100mm, 107mm, 110mm and 114mm. Please indicate size in the "comments box" during the checkout process Balls include 2 with a curved strip (thin parallel lines) and 2 with a straight strip (wider, crisscross pattern) on them All balls are manufactured of durable Partex composition resin material Balls are manufactured to Professional Quality Tournament Specifications