Hockey helmets are the protective gear hockey players wear on their heads to keep themselves safe from the general physicality of hockey. A number of different companies, including Bauer, CCM, Warrior, and Mylec produce hockey helmets.
The helmet itself is made up of the shell and foam padding on the interior of the shell. The shell is made of vinyl nitrile, a plastic-like material. This substance does what any good helmet is meant to do and helps to prevent the force of an impact from being focused in one spot. The foam padding can also be made from vinyl nitrile, but also may be made from an expanded polypropylene foam or other materials.
Helmets also generally have plastic visors or metal cages for protection of the player's face. Where visors usually only extend down to protect the eyes, cages protect the player's entire face.
Despite the physical nature of the game, hockey players did not always wear helmets. When the first helmet was introduced in the 1928-1929 season, it was not widely used. Even in 1968, when Bill Masterson suffered a fatal injury on the ice that could have been prevented with a helmet, the NHL did not require players to wear helmets. In 1979, this changed, but the rule only applied to new players.
Craig MacTavish, the last NHL player to not wear a helmet, retired in 1997, though some players still do not wear visors. Hockey players at the high school and college levels in the United States, however, are all required to wear helmets with cages for full protection of the head and face.