I got the floor mat that was meant for use on a deep pile carpet; even though my carpet is not that thick. This one is super strong and lets my desk (wheeled) chair move very smoothly and should last even longer than the old one. (2 yrs). I had to use a small saber saw to trim off a 12" piece on the end so it would fit in my narrow office space. No problems.
I recently purchased a large desk with a separation and two openings for chairs. It sits on a 3/8" pile carpet. I bought one of these chair mats first liked it so I then purchased another identical one. I bought them on sale so it was a good value. So far they seem to be holding up well quality and thickness are adequate so I'm satisfied.