Overstock drops the price of the Serta Rejuvenator 4-inch Memory Foam Mattress Topper from $157.99 to $89.99 as part of their 25 Days of Deals. With free shipping, that is matches the lowest price we've seen to date. This topper is available in sizes Twin-California King and has a 2.5-inch base layer and a 1.5-inch temperature-sensitive top layer. It is well reviewed with 4.5 out of 5 stars from over 3,000 buyers. There is no sales tax (except UT).