What's the difference between Iwatch 3 and 4?

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Tags

1. #including
2. #claimed
3. #barometric
4. #times
5. #processor
6. #watch
7. #heart
8. #extras
9. #faster
10. #called
11. #altimeter
12. #hardware
13. #series
14. #sensor
15. #optical
16. #upgraded
17. #features
18. #apple
19. #built