Polar T31C Heart Rate Sensor

At the heart of your training is the coded T31 transmitter. Its purpose is simple: to transmit your heart rate to your wrist unit. Slim and light, the ECG (electrocardiogram) accurate transmitter is fully waterproof and designed for all weather conditions and prevents interference or crosstalk from other nearby electronic devices Built to last up to 2500 hours of training usage Prevents cross-talk from other electrical devices for accurate measurement of your training Non user replaceable battery Transfers heart rate information while swimming