Instruct: Classify an Amazon review as either positive or negative.
Query: Nice ball

I am happy with this ball. I sit on it at work for hours at a time. The surface is not slick, it is a bit sticky -- which is great by me. The ball gets a little egg-shaped after hours of sitting on it, but regains its shape quickly after no use for an hour or two. I usually just roll it over after an hour or two and sit on the edge of the 'egg' to return it to round shape while I am still using it.