Polar S3+ Stride Sensor Set 2.4GHz Get a statistical look into your running performance with the Polar S3+ Stride Sensor Set 2.4GHz. This small and lightweight sensor accurately measures each stride you take, helping you analyze the effectiveness and efficiency of your run. The Polar S3 also measures running speed/pace and distance. You're able to review your running cadence and stride length, allowing you to improve running technique and performance. The firm shoe attachment promises accurate speed and distance measurement. Shock and water resistant.