Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Works perfectly

This product keep the warmth well. Some things that may help. Don't try to walk in them, not even one step. Also, I find that heating them 30 seconds and then turning and fluffing them each time creates a more even heat. Don't try to heat them longer than 2 minutes or they get way too hot. Start with 60 seconds and then adjust for the next time.