This thing is AMAZING and has saved me. I recently ordered a new king mattress and it was way too firm, I was getting awful sleep. The first night we got this, I fell asleep and didn’t wake up one time the entire night. INCREDIBLE. Grew to full height within an hour. No weird smell. It’s very deep - I’m 5’2” and 130 - I sink into it a ton. If you don’t want fully “sunken” and surrounded, maybe 2” or 3” for more of a cushion but not fully embraced. You could add this to any mattress and it would be life changing. Highly recommend.