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Polar T31 Transmitter With Elastic Strap Polar A370 Waterproof Fitness Tracker Polar T31 Coded Transmitter With Elastic Strap

Slightly different to the T31c Transmitter, the slim, light and waterproof T31 doesn’t have the benefit of coding for interference free transmission. However, its purpose remains the same: to transmit your heart rate to your wrist unit ECG (electrocardiogram) accurately.

No user replaceable battery.

Waterproof fitness tracker with continuous heart rate monitoring, Sleep Plus sleep tracking and Polar's trusted training features.


  • Wrist-Based Heart Rate
  • Continuous Heart Rate
  • Sleep Plus
  • GPS Via Mobile
  • Daily Activity Goal
  • Sports Profiles
  • Smart Calories
  • Vibrating Smart Notifications
  • Waterproof


Weight:31.7g (S), 37.3g (M/L)
Wristband thickness:13.5 mm
Wristband width:23.5 mm
Wristband material:Silicone
Wristband sizes:S, M/L


  • Waterproof (WR30)
  • Wide-viewing angle full color TFT display with capacitive touchscreen
  • Screen resolution 80 x 160 pixels (RGB)
  • Screen size 13mm x 27mm
  • Polar proprietary optical heart rate module (2 green LEDs, 1 photodiode, analog front-end)
  • Rechargeable 110 mAh battery
  • Battery life up to 4 days with 24/7 activity tracking, including 1 hour of training per day (without smart notifications in use) with continuous HR


  • Easy wireless sync via Bluetooth® Smart with the Polar Flow app
  • Micro USB connector for charging and data sync with PC or Mac via Polar FlowSync

Compatible With:

  • Computer running Mac OS X10.6 or later and Windows XP, 7, 8, 10
  • Mobile phones running iOS10 or later and Android 4.4 or later
  • Polar Balance smart scale
  • Polar H10 heart rate sensor
  • Apple Health Kit, Google Fit, MyFitnessPal and MapMyFitness

At the heart of your training is the coded T31. Its purpose is simple: to transmit your heart rate to your wrist unit. Slim and light, the ECG (electrocardiogram) accurate transmitter is fully water resistant and designed for all weather conditions

  • Built to last with up to 2500 hours of training usage
  • Prevents cross-talk from other electrical devices for accurate measurement of your training

No user replaceable battery.

Polar H10 Heart Rate Sensor
  • The improved electrodes make Polar H10 the most accurate heart rate sensor in Polar’s history.
  • Polar H10 is compatible with top fitness apps, gym equipment and many other Bluetooth devices.
  • You can connect it simultaneously to two Bluetooth devices.
  • The 5 kHz transmission makes sure you can monitor your heart rate even in water.
  • Polar H10 has a built-in memory for heart rate data from one training session. The data can be transfered to Polar Beat, Polar’s free fitness and training app.
  • The new Polar Pro chest strap is comfortable to wear with soft textile material, slip-preventing silicone dots and a secure buckle.

Compatibility iOS mobile devices iPhone 4S and later and Android mobile devices with Bluetooth 4.0 capability and Android 4.4 or later.
Updates Via mobile phone using Polar Flow app or Polar Beat app
Connector size 34x65x10 mm
Weight Connector 21 g (0.74 oz), strap 39 g (1.38 oz)
Memory One training session
Battery type CR 2025
Battery life 400 hours with BLE and 5 kHz transmission active
Water resistance 30 m (Suitable for swimming)
Materials Connector: ABS, ABS + GF, PC, Stainless steel. Strap: 38% Polyamide, 29% Polyurethane, 20% Elastane, 13% Polyester, Silicone prints.
Operating temperature -10 °C to +50 °C / 14 °F to 122 °F