Serta Deluxe 4-Pound 2″ Memory Foam Mattress Topper for $72.99 shipped. Here is a screenshot for reference. It is made of Visco elastic foam and available in King, Cal King, Queen, Full, and Twin sizes. Memory foam is resistant to dust mites and antimicrobial. As a comparison, Amazon has a similar 4-pound 2″ mattress topper for about $149.