Instruction: Evaluate the answerability of a question by analyzing the related document, outputting yes if the document contains information addressing the question, and no otherwise.

Input:
Question: Is the backrest removable? Do I have the option of using the chair without it?
Document: It's hollow vacuum-formed plastic and it begins to bend as you apply pressure. I drilled a hole in the backrest to either fill it with cement, plaster of Paris, or resin so that it might hold up. I'm not sure why you create a product with what is essentially a decorative backrest.Overall the ball chair is comfortable, but it is that much better than just using a single ball itself for 1/4th the price? Not really.
This chair is very comfortable and has helped me improve my posture. It makes me feel like I am working out while sitting at work since I am using more of my core.
I've been using this chair for a couple weeks now. I love it! I have never tried a different brand, so I can't compare the quality, but I feel that it is sturdy and will last me many years.
Ball deflates ever two days without a hole. The seat itself is VERY cheap plastic and creaks and bends. I am not a heavy person but the chair feels like it wants to give way on my weight.... much less a large person.This chair is not worth your time nor do I think ANY chair of this style would work.
I got this when I was going through some unrelenting back pains.It got a brief period of adjusting, because I'm used to leaning against something. But I use this at work all day, everyday without getting tired (I imagine because my core is made of steel now).Not going to lie, there have been too occasions where the chair did not want me on it, and as soon as I bounced onto the chair, I bounced right off.
This is a great chair to use while working at your desk. I love the fact that it helps you with your balance and posture, all while working on your core!
This a comfortable chair and sturdy. I feel safe sitting in it. Easy assembly. The price was very reasonable. Good quality.
feels great, can excersize my back while sitting on it. I bought teh ball chair height adapters because i am 6'1&#34;. it helps alot.
Wrong ball size came with the chair. It is very comfortable, but bad for my knees to bent and it does not sit high enough for my desk (even with the risers I bought separately.
I ordered this ball chair to use for a variety of exercises and demonstrate better ergonomics to others. I love this chair and wish all classrooms had these chairs! Recommend this chair!
Answer: yes