Bests & Worsts Reviews from Amazon

This bottle warmer is really a thermos that holds 2 cups of hot water and a very large cup in which to pour the hot water. For travel, the thermos locks inside the cup. I microwaved 2 cups of water for 3 minutes in a Pyrex cup then poured it into the thermos and then locked into the cup. 13 hours later, it was still hot enough to warm a 4 ounce bottle of cold breast milk in a couple of minutes. I would highly recommend, however keep on mid that it's larger than you think and WILL NOT FIT even the large cup holders in your car. My husband loves it because he can easily feed the baby on the go without having to come home to warm the breast milk. UPDATE: After a few months of occasional use, I noticed a couple of rust spots inside of the cup. I always hand washed it with a baby bottle brush. I guess, it’s not a big deal since the water never mixes with the breast milk. However, I would caution against using to keep water warm for making formula.