Dudley WS12 RF40 ASA Slowpitch Softballs - You have got to have reliable balls to play this game. Get the Dudley ASA Yellow Synthetic Softball. These slowpitch softballs have a synthetic cover, poly center and offer a COR of .40 with a compression of 375 lbs. When you play, use the Dudley ASA Yellow Synthetic Softball. Sold by the dozen. Sz: 12".