I upgraded to a fancy memory foam mattress (the Allura) with a very thick mattress, so I needed them. These cheery sheets are more than ample for that type of mattress. I had read all of the reviews about the pros and cons of the thick mattresses and concluded that 300 thread count in sheets is sufficient to let my body breathe while sleeping on foam (which is toasty in the winter and a sauna in summer). These sheets are sturdy enough to be my only covering in summer! Note that I am handy with a sewing machine; I added six inches of fabric to the bottoms of my two favorite King fitted sheets to accommodate the new mattress and it took half a day to do a shabby job. Ask yourself whether your time is worth more than the price of these deep-pocket sheets?