Fitbit Alta Black Fitness Wristband

Get the power of continuous heart rate in Fitbit's slimmest design yet-all day, during workouts and beyond. Sizes - Small: 5.5–6.7 inches(140 mm–170 mm), Large:6.7–8.1 inches(170 mm–206 mm), X Large: 8.1–9.3 inches(206 mm–236 mm) With heart rate, you can better measure calorie burn, and use zones (fat burn, cardio, and peak) to find the right workout intensity for your goals With sleep stages powered by PurePulse heart rate, automatically track your time spent in light, deep and rem sleep and take steps toward a better night's rest. Syncs with Mac OS X 10.6 and up, iPhone 4S and later, iPad 3 gen. and later, Android 4.4 and later, and Windows 10 devices. Syncing range- Up to 6.1 m See how working out more can improve your health by comparing your resting heart rate trends to your activity. Operating temperature: 14° to 113° F, Maximum operating altitude: 30,000 feet Automatically track your steps, distance, calories burned and active minutes The minimum and maximum circumference range between 140 - 170 millimeters gently use smoke free