Any time you have a chair that rolls on carpet numerous times you need this type of mat. Not only does it make the chair easier to move but it save your carpet from excessive wear.
It is not rigid. It gets indentations where the chair castors are and over time they get worse because the chair castors will tend to end up in those indentations repeatedly. I will be returning this item if I can find a better one. I never had this problem with my old chair pad which came from Staples.
It fir well under the knee-well. It seemed to protect tghe carpet. It was a see-thru panel. However it seemed to be too light duty for the servic. That ios to say the indentations under the chair's wheels were very noticable. We think the plastic will not lasat long.