A common nickname (common if you lived in 1940 I suppose and also call $10 bills "sawbucks" or the telephone "the Ameche") for baseball was "horsehide", which not surprisingly comes from the name of the material used on the outside of the baseball. Except in 1974, Rawlings started using cowhide on its baseballs that it made for MLB. However in Japan, horsehide is still the material of choice.
But for the WBC, Asian pitchers are going to have to use a cowhide baseball. The cowhide balls tend to have higher seams and a large supply of the balls was shipped out to the competing national teams to give their pitchers time to adjust.