Item arrived neatly boxed, hard as concrete. You have to unseal and allow it to expand on its own, which doesn't take long if your room is warm. I detected no odor after allowing it to air/expand for a few hours. I placed it on the bed that night, and it's been heaven ever since. LOVE, LOVE, LOVE IT!!! BUT......I purchased the 4" to make my Sleep Number more tolerable. That did not work. So, I trashed the Sleep Number (should have done that sooner) and bought a gel infused memory foam mattress, and placed the topper onto it. The mattress I purchased was firm, and this topper was the icing. Haven't slept this well in umpteen years. My husband and I love our mattress/topper set now. He loves a firm bed, and I love a soft bed. The topper made our set a firm soft, if that makes any sense ;) The bad, I hate the toppers' cover. It kept riding up off the mattress, so I did replace that. I do have another memory foam mattress set that is way more plush, (more expensive as well) I tried the topper on it as well. Horrible. Made the bed way to soft and cradled our bodies like we were in a taco shell. Extremely difficult to roll over and also to get out of the bed. Summing it up, the 4" topper is excellent on a FIRM bed. Did I say WE LOVE IT? I rather sleep on the lower price memory foam mattress, with this topper, rather than our much higher priced plush memory foam mattress. I cannot say enough about how great our firm bed feels with it. I do not recommend if your trying correct or make a lumpy mattress, like a Sleep Number, sleep better. Do not recommend if your mattress is already soft, simply because you will sink/sag even more. On another note, to fully enjoy a gel mattress/ topper, be sure to find yourself a few GOOD memory foam pillows...just saying......'