The first one that was delivered came extremely warped so I returned it to the store. In the store they suggested leaving the mat in the Georgia sun on a concrete surface in order to flatten it out. Next time I ordered one it worked!
I use this mat in my home office where I spend a lot of time at the computer. The mat is now less than 2 weeks old and dented all over from the chair's rollers... oh well I guess you get what you pay for. I have my doubts as to how long it will last. The one I replaced lasted 5 years...