There is one vibrating motor in the external stimulation nub. We us the space in the shaft of the vibrator (the part used for internal stimulation) to store the sensors and extend the battery life.
You can adjust the vibration settings in the sync tab of the Lioness app.
Pro-tip: try setting one vibration setting to 0 to experiment with the Lioness without vibration! Click here for more ideas for using the Lioness.