2 players are standing in front of each other at a distance of 1-2 meter.
Each has a ball.
A throws her ball up in the air, B throws her ball to A (2-hand throw), A catch the ball (2-hands), returns the ball to B and catches her own ball again.
At once she throws the ball up in the air and so on.

They must not throw the ball high up in the air.
The exercise is made to make the players fast in passing and returning.