In my opinion (for what it's worth), this is your standard thermal cup/mug. It will fit under a Keurig machine if you remove the base. Do make sure you get it under where the coffee or tea is going to come out.
As far as keeping your coffee or tea warm, mine has done a fine job of it. Also, it has a band around it so, you don't have to worry about your fingers get heated by the heat of the hot coffee or tea.
Overall, it's a good solid thermal cup/mug. If you want one you can be certain will work with your Keurig machine, this is the way to go.
I don't know if there are any Keurig machines it won't work with. To be on the safe side, you may want to double check on that before you purchase one of these.