We have been very pleased with our king size 4” gel/pillow-top memory foam topper. If you decide to go that route we found the neatest trick for cutting to size! We traced the original TT mattress size on to the foam. Then we used an electric kitchen knife to do the cutting (picked this up from a YouTube video like the one linked below). It cut the foam like a hot knife on butter and the topper fit the mattress perfectly.