This deal has ended.
Overstock now has the Serta Ultimate 4" Memory Foam Mattress Topper in all sizes for $159.99 after a BradsDeals Exclusive $20 discount valid through 5/9 reduces the price. Plus, shipping is only $1 through 4/30 (otherwise $2.95) and there is no sales tax (except UT, IN). Over 700 Overstock reviewers have rated this a 4.5 of 5. Serta is the best brand and 4" is the largest size in memory foam.