Markwort Corkballs. Hitting a corkball is one of the most effective baseball hitting drills. So stop the wiffle ball, sponge ball and all other backyard baseball games and start playing Corkball. You will not only have fun playing corkball, it is one of the best baseball training devices you can do to improve your hitting skills. Sharpen your hand-eye coordination and pick up flight and spin off the bat by practicing with corkballs. The corkball's size increases your concentration level and eye sharpness as well. It is a great hitting tool that can be used in your school gym when the batting cage is not available. Corkballs are great when there is no field to take pre-game batting practice. Simply go out into the outfield and give your team the pre-game swings they need. Leather cover, official size 1.6oz., 6.5" circumference. Color: White.