Baseball Batting Helmets
You'll see offensive players, whether at-bat or running the bases, wear helmets to protect their heads from being hit with the baseball. These helmets are made of plastic with a foam interior and has an extension (called an earflap) to protect the ear that is facing the pitcher's mound when the player is at-bat. Younger players might have a facemask attachment for extra protection. Helmets weren't required by the MLB until 1971, but it's best for even the most experienced players to wear them to prevent head injuries. A 90 mph fastball straight to the head would not be very pleasant.