content: This functions more as a 'slow-downer' of your coffee cooling off. (Say that 3 times fast.)Pros:Doubles the life of your cup of coffeeWarms up quicklyIt's a trooper, after a year, gets just as hot, just works.Cons:Never turns off, ever, I've left it on at the office over the weekend, it should have some kind of safety auto-off after a couple hours or so.Coating on the surface not very durable, after about a year it looks pretty bad.Notes: Your mug choice is important, I noticed a large improvement changing from a clear-glass mug to a regular (ceramic?) mug.