For measuring heart rate, speed, and distancePolar Equine RS300X G1 gives you all the essential heart rate features, a Polar Equine T54H coded transmitter, and speed and distance measurement with the Polar G1 GPS sensor. Only by combining these three, you can truly make sense of your training. Polar RS300X training computer Polar Equine T54H coded transmitter Polar G1 GPS sensor Note: Also available without G1 GPS sensor