Microsoft Band helps you live healthier by tracking your heart rate, exercise, calorie burn, and sleep quality, and helps you achieve more with email, text, and calendar alerts at a glance. Advanced sensors track data specific to running, biking, and golfing. Technology from Microsoft Health gives you actionable insights based on your data. Works with Windows Phone, Android, and iPhone.*Size Large fits wrists 7.3″-8.5″ Continuous heart rate monitor tracks your heart rate, calorie burn, and sleep quality. Works with Windows Phone, Android and iPhone* Get email, text, calendar, and call alerts on the go Tracking for running, biking, golf, and more