I measured my mattress and the topper before I ordered this set. It measured 16 inches. The set reads 18". The first 3 corners fit beautifully...the fourth corner the set barely went over the corner to just hang on to the edge.
The set says 400TC...I thought great this would be even softer than my 320TC sheets..well sadly they arent even as soft. I would not recommend buying these sheets, they do not fit true to size.