Mat was shipped folded up. After laying in the sun and then indoors weighted down with books for 36 hours I finally am able to use it but it is still wavy. Seems heavy enough to do a good job if it ever lays flat.
I have only used it for a few days now and it is already becoming "dimpled" where my chair sits.....and then it is aggrevating to have to push yourself out of it (like getting your car to back out over a small snow drift that the plow left at the end of your driveway!)