GB (gangbang) refers to group sex involving several male participants and one or a few sex workers. In Switzerland, it is offered as an event at specialized clubs (registration requires a negative test result) or as a private booking by several clients who are friends.
High safety requirements: mandatory testing (often with a 24-hour window), strict condom use, clear stop codes, presence of a supervisor, and a limit on the number of participants. Premium rates apply accordingly.