I have looked for years for 100% cotton percale (not sateen weave) fitten twin extralong sheets.  AFter ordering and returning at least a dozen sheets, which did not fit the deep mattresses as advertised. I had just about given up until I tried these fitted sheets.  LOTS OF ROOM TO SPARE with these, and the cotton is what you want from percalecrisp, 400 TC, and nicely made.  They wash like a dream and come out of the dryer unwrinkled.  I bought EIGHT more for our beds.  because they are impossible to find and these are SO WONDERFUL.  Who would have thought a sheet could make a difference?  They do!