Polar Loop Crystal Motivates you to reach your daily goal by tracking your steps, distance, and calories burned 24/7 Vibrating inactivity alerts help you keep moving throughout the day Automatically tracks your sleep time, quality of sleep, and sleep patterns Compatible with H7 Heart Rate sensor for continuous, accurate heart rate Syncs with free Polar Flow app and web service for additional workout planning, motivation and guidance Water Resistance: IPX7 Wristband Size : 9  . NOTE - Measurements taken from the LAST HOLE to the END OF RUBBER next to buckle (not from end to end). *Loop is from end to end prior to cutting.