What does it take to be a ball boy?
All week the best tennis players on the planet have been battling it out at the ATP World Tour Finals in London.
On Sunday Novak Djokovic and Roger Federer face each other in the final.
Ricky went along to the North Greenwich arena to find out more about the event.
He also found out if he had what it takes to become a ball boy at the ATP World Tour.
The grand final will be shown on BBC Two at 6pm on Sunday.