4 PIECE BED SHEET SET: 2 pillow cases and a flat sheet and fitted sheet. 100% Microfiber, 1800 Threadcount!!! DEEP POCKETS/ EASY FIT: They fit mattresses up to around 16 inches deep. If your mattress is smaller than 16 inches it will fit just fine. A lot of mattresses are pretty big these days and we feel this is a good universal size that fits most mattresses