Corkball - Hitting Drill Balls Corkballs are designed to improve a baseball player's hitting skills. Corkballs can be used for small playing areas and indoor training during winter months. Corkballs are virtually indestructible and can be used on wet field conditions when traditional baseballs can not be spared for batting practice. Corkballs sound just like a real baseball when hit, making batting practice more enjoyable. Corkballs can be thrown straight, or made to curve, dip and dive, simply by gripping the Corkball in various positions.