flex Wireless Activity and Sleep Wristband, Black. Tracks steps, distance, calories burned and active minutes. Monitors how long and how well you sleep. Silent wake alarm. LED lights show how your day is stacking up. Comfortable wristband. Syncs with select mobile devices and your computer. Set goals, view progress and earn badges. Share and compete with friends. Free iPhone and Android App. Water resistant. Includes large and small wristbands.