The Corinthian helmet was the standard helmet used at the beginning of the phalanx. This helmet provided excellent defense because by protecting the head, an area the hoplon could not. The Corinthian helmet completely enclosed the head leaving only slit in the front so a hoplite could see and breathe. However, this form of helmet sacrificed hearing and severely peripheral vision at the cost of protection. This meant that in order for the phalanx to operate well together, they had to be well trained and disciplined. The Corinthian helmet would be very difficult for a hoplite to use in battle outside of a phalanx because of the vision and hearing limitations. As time went on, the helmets became more open, eventually leading to the bell-shaped helmet called a Pilos that does not restrict hearing or vision at all.