This coffee warmer also came with an aluminum pad for coffee mugs with concave bottoms, for dispersing the heat evenly, which is a really good thing since most of the mugs out there don't have flat bottoms

Not a good thing to leave an empty cup on this product.

The aluminum disc is a useful thing to have with a mug warmer since all of them out there are designed for flat bottomed

This has been the best thing I have bought in a long time, and I would recommend it to anyone!