Instruct: Classify the given Amazon review into positive or negative sentiment.
Query: AMAZING

I don't know how these work, but they're amazing. If you're choosing between this and the hand-size version, keep in mind that these last almost twice as long. The downside is that you'll use them up faster because you need one for each pocket. Sometimes they have a tendency to get too hot though, which isn't a problem for me, but I wouldn't give them to young kids or elderly, and I definitely wouldn't fall asleep with one touching your skin. Also, they really do last around 20 hours in case you're skeptical!