I was so disappointed to open this Christmas gift after using my 14 oz Ember mug almost every day for a year and find out this tumbler is completely metal inside!! Somehow I missed this in the description. I never would have dreamed a “ceramic mug” known company would do that. 
I never even plugged it in. Started return & right back in the box it went. I have plenty of metal coffee mugs  that I don’t care to drink from vs ceramic. Gave 2 stars because, if you don’t mind the tastes of coffee from metal, it’s a nice container.