Dudley USSSA 12" Thunder Heat Slowpitch Softball You have got to have reliable balls to play this game. Get the Dudley USSSA Yellow Leather Softball. These slowpitch softballs are the official ball of USSSA conference tournaments, World Series and Home Run Derbies and have a leather cover, poly center and offer a COR of .40 with a compression of 325 lbs. When you play, use the Dudley USSSA Yellow Leather Softball. Sold by the dozen. Sz: 12".