Ultrasound gel is important for the doppler's ability to produce a clear sound of your baby's heartbeat. It acts as a conductive agent, ensuring that there are no air bubbles between the probe and your skin so that your baby's heartbeat comes through loud and clear everytime.

Your doppler rental comes with one large 100ml tube of gel but If you are planning to keep your doppler more than a month or two, you may want to purchase a few extra tubes so that you dont run out.