Do not buy this device EVER, the idea is perfect, but Garmins execution of this device is so poor, that it will screw up Your training leaving you sad, angry and ~450$ poorer.
This device crashes, and you loose your valuable data. After every crash, statistics such as "training effect" resets. So if You run 30k, and it crashes at 28, the Watch will assume you ran 2k.
Garmin, do you have any idea how valuable this data is for us serious Runners? Of course You do, since You invented it. Do You know how negatively Your Garmin brand is affected when You make customers pay ~450 $ for a device that messes up their valuable data. How dare You release a device that does not work.
Furthermore the GPS works worse than on my 620 Garmin, which I had prior to this. When i run in the Woods I had no problems with the 620, with the 645M I get the weirdest slowest times ever. Even if I activate both GPS and GLONASS.
Today I ran my longest race for this year, a 30k trailrun called "Lidingoloppet" in Sweden, it cost 96$ to participate, I trained for 6 months for this. And Your stupid device crashed twice. How do You think those crashes affected my joy of competing after training. It was a terrible downer Garmin! Twice! Thank You so very much! what am I to do now?
I am gonna sell Your stupid Garmin device, and go to one of Your competitors, that is what I am going to do.
Your Garmin company does not deserve Money and success, when You steal 450$ from Your loyal costumers with a device that does not work!
And if You browse the net, and even this forum, You will see this it not my solitary rant, there are a bunch us of that has gotten fooled, and it is a lot of Money!
How dare You, shame on You Garmin!