Review on NG1702 - Mustard USB Cup Mug Warmer Coaster in Dark Brown Hot Cookie by Steven Barbon

Should have read the reviews before buying. I've tried several coffee mugs/cups, some have a flat bottom but most have a concave bottom. NONE of the coffees were warm enough to drink after being set on the USB cookie warmer for about 30 minutes. Now I'm hesitating between sending it back and saving. The only thing I would leave is that this is a very nice coffee warmer.