I bought king size sheets for my king size Tempur-pedic mattress. These sheets are so stretchy that they clump up in sections and create a wrinkly, bunched-up mess. I cannot seem to find any sheets that fit tightly and crisply on my bed. I have purchased other Tempur-pedic sheets that fit a little better but most sheet sets seem to be made for extremely deep mattresses and do not fit tightly.