The Stride length sensor with Bluetooth® Smart is for runners who want to improve their technique and performance. Track your speed, distance and stride length with compattible sports watch or the Polar Beat app, whether you are running on a treadmill or on the muddiest trail. Attach the Stride length sensor to your shoe and enjoy your training!• Compatible with dozens of leading fitness apps, including Polar Beat
• Measures each stride you take to show your running speed and distance
• Helps improve your running technique by showing your running cadence and stride length
• Shows how your running performance changes with Polar's unique Running Index feature
• Fits firmly on your shoelaces thanks to its compact size
• Shock and water-resistant to handle even the most demanding runs
• Compatible with iPhone 4S and later