Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Keeps It Hot

Excellent beverage carrier and it does not leak. Also, the flip top says up when you're drinking. When pre-warmed, it will keep coffee hot for approx. 4 hours. Only surprise was a small air vent in the rubber base. If you immerse the bottom in water to wash it, the base fills up with water and you'll wonder "where the leak is".