Instruct: Classify the given review into positive or negative sentiment.
Query: PERFECT FOR THE AIRPORT

The .5L is the perfect size for plane trips. I keep it empty in my carry-on until I pass security then fill it up at the water fountain. No more paying for bottled water at the airport and environmentally friendly too. When empty, the bottle takes up no room - you can't say that for any other water bottle on the market!