To facilitate and safely offer certain classes, an external instructor is required. In these cases a small amount will be asked for, which must be handed in cash to the instructor at the start of the class in order to partake in the class.
If the class costs a little extra, it will be shown on the class timetable online and outside the class studio.
You would book these classes like any other class, in the booking section of your Member's Area or app, and then payment is taken when you arrive.