A Work of Art on Your Wrist:The large 1.39″ AMOLED high-definition screen with 326 PPI pixel density is clear and vivid. Dozens of different styles of watch faces are available, with matching always-on displays patterns, enabling you to view the time even when the watch’s other features are inactive, and making your Amazfit GTR 2 a unique masterpiece of change and creativity. Stay Safe with Elevated Heart Rate Alerts:The Amazfit GTR 2 is equipped with the Huami-developed BioTracker 2, allowing it to perform 24-hour heart rate monitoring. It covers heart rate zones and provides warnings when your resting heart rate is abnormally elevated, keeping you aware of the exercise effect and reducing exercise risks. Blood-oxygen Saturation Measurement:SpO2 is a major indicator of human health, so the Amazfit GTR 2 introduces an SpO2 monitoring function. When you engage in sustained mental labor, run a marathon, or do intense outdoor exercise, you can test your SpO2 level the moment you start feeling unwell to get a better understanding of your physical condition.  One Score to Summarize Your Physical StatePAI (Personal Activity Intelligence) is a science-backed health score, which measures the impact of physical activity on your heart by processing data about your heart rate, exercise time, and other complex health information with an algorithm, to provide a single-value score unique to each user’s experience, for easy understanding of their physical state.  See Sleep Stage and Nap Data:The Amazfit GTR 2 supports in-depth sleep monitoring, which can accurately differentiate between the light, deep, and REM (rapid eye movement) sleep stages, monitor the sleep breathing condition, and provide analysis and suggestions for improvement based on a night of sleep. The watch also recognizes naps over 20 minutes in order to record more complete sleep information. Monitor Your Stress Levels:Check your personal stress level – relaxed, normal, medium or high – anytime you feel pressured throughout the day, so you know when to relax and reduce it.  Your Playlist on Your Wrist:Control mobile music playback through the watch via Bluetooth, or transfer 300-600 of your favorite songs to the watch through your mobile phone, with a massive 3GB of local music storage. Put your phone down, your Amazfit PowerBuds wireless headphones on, and listen to your favorite playlists while you exercise, anytime and anywhere. Bluetooth Call Function and Offline Voice Assistant:After connecting your Amazfit GTR 2 to your mobile phone, the Bluetooth call feature lets you answer calls on your watch via the built-in microphone and speaker. You can also perform voice operations on your watch without internet access through the offline voice control feature including turning on sports modes or opening the heart rate monitoring function.  Powered for Maximum Performance:Featuring a more sophisticated circuit design, a thinner body, and a high-capacity 471 mAh battery, the GTR 2 boasts a battery life of up to 14 days with typical use. With this extended battery life, you are covered wherever your exercise takes you.  Specifications Brand: Amazfit Model Number: AMZGTR2 Model Name: Amazfit GTR 2 Color: Thunder Black&Lighting Grey Touchscreen: Yes Water Resistant: Yes Water Resistance Depth: 50 m Usage: Fitness & Outdoor Dial Material: Stainless Steel Other Fitness Features: Activity Tracking (Heart Rate, Distance, Step Count, Calorie Count, Blood-oxygen Saturation Measurement (SpO2), Sleep (Light, Deep, REM and Sleep Stages), Stress Levels (Relaxed, Normal, Medium or High. Battery: Lithium-Polymer Charge Time: 150 Mins Battery Life: Upto 10 Days (Based on Usage) Rechargeable Battery: Yes Charger Type: Charging Base Other Features: 3D Curved Bezel-less Design, Music Storage and Playback, Bluetooth Phone Calls, Online and Offline Voice Assistants (Only Supports English Voice Commands), Built-in Alexa Support, High Capacity 471 mAh Battery, Massive 3 GB of Local Music Storage Thickness: 10.7 mm Diameter: 46.4 mm Weight: 31.5 Grams Sensors: BioTracker 2 PPG Bio-tracking Optical Heart Rate Sensor, Accelerometer Sensor, Gyroscope Sensor, 3-axis Geomagnetic Sensor, Ambient Light Sensor, Air Pressure Sensor Compatible Device: iPhone, Android Smartphones Notification: Yes Notification Type: Vibration Call Function: Yes Bluetooth: Yes Wi-Fi: Yes GPS: Yes Bluetooth Version: 5.0 Operating Range: 10 m Call Features: Take, Answer and Reject Calls Display Resolution: 454 x 454 Pixels Display Size: 1.39 inch Display Type: AMOLED Backlight Display: Yes Scratch Resistant: Yes Other Display Features: Always-on Display, HD AMOLED Color Display (326 PPI Pixel Density)