Looks like Elle and Sadie are playing the guess the voltage game. It's a simple game, one girl repeatedly shocks the slaves cock and balls with voltage and the other girl tries to guess at what level the shocker is set at based on the screams of the slave. It's a fun game that can sometimes last a long time as the girls occasionally lose track of time when they are having so much fun . You do have to feel some pity for the slave though as clearly he is enduring a horrific level of pain.