Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Very convenient when traveling

I just came back from a road trip and this came in very handy. I have reheated the pack back to its original state time and time again and I'm still happy with its performance. It really does get quite hot. The only complaint I would have is that it doesn't heat the bottom of the bottle so it probably takes a little longer than I would have liked. But it does what it's supposed to do and works great on baby food jars as well. If you're heating cold milk bottles, however, I would use 2.