product details-used works great Add this Fitbit Flex 2 fitness tracker to your weight-loss tool set. It tracks your movement and calories burned, and you can set alarms to remind you to exercise or eat right. Track steps, distance, calories burned and active minutes Ultra-thin, removable tracker hides in bands, pendants and bangles, The Fitbit Flex 2 wristband is made of a flexible, durable elastomer material similar to that used in many sports watches. It also has a surgical-grade stainless steel clasp Swim-proof for tracking swimming, life-proof for wear in the ocean, shower, pool and beyond SmartTrack automatically recognizes select workouts and records them to your Fitbit app; Get call and text notifications on your wrist with unique vibration patterns and color-coded LED lights Automatically track how long and how well you sleep, and set a silent alarm to wake with a small vibration; An LED display lights up when you get calls, texts and Reminders to Move, and shows you how close you are to your daily goal with a simple tap. Operating temperature: 14 degree to 113 degree fahrenheit, Maximum operating altitude: 30,000 feet The minimum and maximum circumference range between 140 - 206 millimeters info: