800 Thread count, 100 Egyptian cotton waterbed sheets for your water mattress. This cotton water bed sheet set comes complete with one flat sheet, one deep fitted sheet and two pillowcases. The fitted sheet is similar to the flat sheet except it has an extra triangular fabrics sewn at the four corners and both flat and fitted are sewn together by the footer so bed stays made. The extra triangular fabric sewn at the four corners in the fitted waterbed sheet are turned over the corners of the water mattress and that is how you dress your sheets on your bed.