Review on ☕ Coffee Warmer Plate – Electric Mug Warmer for Home or Office Desk, Keeps Beverages Warm, 4.5" Diameter (Wood) by Barbara Zepeda

This mug warmer is great when you can find a perfectly flat bottomed mug. Unfortunately they are very difficult to find. Almost all mugs are concave at the bottom to some degree, and unless the outer rim of the mug is in contact with a heating pad, those things are pretty much useless. To solve this problem I found metal washers in the garage and stacked them on top of the heater to fill the gap and make contact with the bottom of the cup. This is VERY helpful in keeping contents warm, although it never gets hot. If a manufacturer ever releases a heating pad with a slightly convex surface, they're going to ditch all those flat heating pads! In the meantime, this thing does what it's advertised to do - heat up. Whether your cup fits the design depends on the consumer.