Hi GKZA3
The Friends Day Pass is valid for 2, 3 or 4 people travelling together. For the return journey, it can also be used by one person travelling alone. It costs a flat rate of CHF 80 in 2nd class and CHF 120 in 1st class, regardless of the number of passengers. The Friends Day Pass is only valid if all passengers are in possession of a Half-Fare travelcard or are under 16 years of age on the day of travel.
You can find more information about the Friends Day Pass under the following link: Day Pass for Friends conditions | SBB
Have a nice day, StéphanieB