Katrin's gym-ball-facesitting workout.

The slave is on a gymball on his back, ready for Katrin to play with him.
She steps over him, decends her ass on his face, then she begins to ride and bounce on his face.
Occasionally she changes the direction and bounces now foreward.
He has to balance on the ball and, offcoarse, fight for air, Katriins big ass seals properly his air-supply.