Difference: Screen size: 1.44inch(t500)1.54inch(x8)1.75inch full screen(x8 plus) t500 app:fitpro x8 and x8plus app :hryfine Specificaitons: Support Bluetooth call, heart rate, can replace 44mm strap, 12 watch faces, step counter, fruit 4 generation size Platform MTK2502 Main screen 1.54 HD IPS, 240*240 Touch screen 2.5D fox surface capacitive full-fit touch screen Bluetooth remider: SMS SMS WeChat QQ news and other client information and other timely reminders Heart rate detection Heart rate monitoring, monitoring your heartbeat around the clock Pedometer, sports calorie, calorie consumption, exercise mileage record Sedentary reminder to get up and change the unhealthy lifestyle Sleep monitoring Objective Science Quantitatively record and analyze your sleep status Find mobile phone function Anti-lost reminder. Two-way search Bluetooth music playback Control mobile music playback Call reminder support Bluetooth function and version 3.0, 4.0 support Bluetooth call Battery specifications and capacity 210MAH high capacity polymer Vibration motor support Other features Alarm clock, calendar, stopwatch, computer Multi-language pack Chinese, English, German, Spanish, Italian, French, Portuguese, Russian, Polish, Turkish, Arabic, Hebrew, Indonesian, Persian.