Not bad, thin but very even material. UNFORTUNATELY fulfillment(?) dept. shipped it in a flat box, where it was loose and could rattle around. It has several creases in it making it “not flat.” Trying to remedy with hair dryer and heavy Webster’s American Dictionary. If that doesn’t work … hi-ho, hi-ho, off to Support I go. 
Or maybe roll it up with a strap, and leave it in the garage to let the mid-Atlantic summer heat do its magic.
I put mine under my mattress for 2 days and that worked well.
I just got mine and have the same problem - they shipped this thin, plastic sheet in a giant, flat box. Maybe I’ll leave it out in the sun for a little while…
Aw man, sorry! Pls reach out to CS to make it right:
Please reach out to Woot! Customer Service. To speed things up, let them know if you prefer a return/refund or a replacement (if possible).
Please allow 24-48h for them to respond.
Self-Return: Items without Li-Ion batteries can be self-returned within 30 days. Go to your Order Details to get started. The return label will be emailed from UPS.
Browser: Use the Woot! Customer Service form
Woot! App: Choose Account from the bottom navigation and then Support.
Note: Woot! Customer Service replies go to the email address on your Woot! account, not your Amazon login email if used/different.