I replaced a very sturdy and thick mat that I had for a long time which held up well. I know from experience that the cheap thin mats are junk and crack quickly. After much research I selected this one which is about as thick as you get without breaking the bank. It was shipped in a big box somewhat rolled up. For my needs it looks to be the right mat time will tell if it holds up over the long term. No smell and it unrolled flat without too much effort. For the price you should be happy with this one it is a little larger than the other to make sure it fits you can't trim this easily.
This is a replacement for a similar mat we had for a few years. It is not terribly rugged but works for our purposes. Not quite sure how to remove the tabs on the edge used to hang it in the store!!
I measured my carpet as directed and chose the low-pile based on that. This mat is too soft for my carpet and the wheels on my desk chair sink in creating divots that it's hard to wheel out of. I stopped using it after a week and it's now sitting on my cellar's cement floor.