Excellent "REAL" Memory Foam!
I did a ton of online research about mattress toppers and ultimately hose this Serta one based on specifications, reviews and price.
I opened it up and let it "self-inflate" on the floor for about a week (I was busy with other things). It rose fully to 4 inches as it should. I honestly don't think this is made by Serta. As others have said looking at the boxing and packaging it appears to be made (in USA I think) by some "generic" manufacturer and upon packaging it they throw a random piece of paper in the box with the "Serta" name on it. My guess is Serta makes a few bucks off each one in return for use of their name. But if that is the case...one could safely assume that Serta feels confident enough to loan the name & reputation on it, right??
I read some reviews that quite often toppers are sized to small to properly fit onto the mattress so I ordered a queen size and cut it down width-wise to fit my mattress. I used a straight edge, a Sharpie marker and an electric knife and it cut smooth and easy. I am tall (6'1") so I did not cut it length-wise and I gained about 3" in length on my full size mattress (sheets and mattress pad all fit fine). By purchasing a bigger size I now have full coverage including added length. Interesting though, a queen size topper should be 6 inches longer than a full size, but this topper was only 3 inches longer (which is why I didn't cut it lengthwise). But...If I did in fact put this queen size topper on a queen size mattress it would've been about 3 inches to short.
First night I slept on it it did give off some "medium" chemical odors, even after sitting opened on a floor for a week. By the 2nd and third night all odors were completely gone.
The topper itself is wonderful. It seems to be "true" memory foam, 4 pound density. It is soft and mushy feeling to the touch but is very supportive and feels firmer when you're actually sleeping on it.
The reason I say it seems to be "true" memory foam is if you press your hand into it you can fully see the whole impression of your hand and fingers for a few seconds. I noticed just about all memory foam toppers (and mattresses) show a picture of this "hand print" in their descriptions but many of them do NOT leave impressions like this (matter of fact if you look around on the big shopping sites you'll notice that many companies use the very *SAME* "generic" picture on the hand-impression test. Its almost like they all found the SAME picture on Google images and cut and pasted it into their descriptions! But either way, THIS topper truly passed that "hand impression test". Also, the topper rebounds pretty darn quick after rolling over in bed or sitting on the edge of the bed.
Long story short, this seems to be a great topper for the money. I Handle it with care to prevent damage/tearing.
Good luck with yours, buyer beware.