The suit has to be able to sustain a constant pressure of 3.5 pounds per square inch so that Felix does not suffer from the bends. Also, the pressurized suit preents Felix from suffering from ebullism. Ebullism is when the liquid in human tissue turns into a gaseous state and expands. This is incredibly lethal and the constant pressure of the suit prevents it from occuring.
The visor had an independent sunshade so that Felix would be able to adjust the sunshade as he needed to. The visor also had an integrated heating mechanism which was designed to prevent fogging and icing, but unfortunately Felix had fogging issues during his descent. Also the suit had cool air and warm air pumped into it during his ascent. The warm air would prevent Felix from becoming cold-soaked, while the cool air was used to prevent fogging via persperation.
The suit involved CYPRES 2 technology(Cybernetic Parachute Release System). This technology is an automatic parachute release system that was designed to work at all points during the fall. The system was set to release at a predetermined altitude if the primary parachute has not already been deployed.
The cameras that Felix wore on his body had been specially tested. They were also specially made. This is because cameras have a hard time working in extreme heat, cold, and in a near vaccuum.