Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Great Office Chair!

I bought this Yoga ball for the main purpose of being my "chair" in the office. It works great! This 75cm size was perfect for me (height around 5'8"). Didn't deflate or have any odors, and if you like a more firm seat you can probably just pump more air into it with the provided hand pump that comes with it. I've been using it for about 2 months now and have not had any problems with it :)