The halo design is consistent across all cars, although each team has a small degree of freedom to add fairings to the outer halo to aid with aerodynamic air flow. A lot of people didn’t like the halo when it was first introduced because it was unattractive, affected the dynamics of the cars and people were unsure of how much it would actually help.
The halo adds 7kg of weight to the car and affects the airflow around and into the car. Teams had to minimise the aerodynamic losses of the turbulent wake flowing into the engine air intake and onto the rear wing and additionally, redesign the monocoques (chassis).
This was a lot of changes to make, and expensive ones, however since 2018 it has saved drivers lives through potentially fatal crashes. In the second to last race of the 2020 season, in Bahrain, Romain Grosjean endured one of the most terrifying formula 1 crashes.
He experienced 67G and 27 seconds within a blazing fire. Grosjean’s car struck the race barrier at a speed of 192kph, tearing the car in half with the front of the car wedged within the barrier. The halo protected Grosjean’s head as the barrier consumed the car. He was so incredibly lucky to walk away from the crash with only burns on his hand.