Slim, lightweight and completely waterproof, the Polar T31 Non-Coded Transmitter and Belt Set accurately transmits your heart rate data to your Polar wrist-top computer. As a result, it’s easy to monitor your heart rate during training runs. This version of the T31 is non-coded. If you’re concerned about crosstalk from other electronic devices, Polar sells a coded version of the T31 as well. Included transmitter belt which works with all current Polar wrist-top computers.