The extra-fine fiber blend is a mixture of high-quality fabrics that are double brushed, cool, and hypoallergenic. This wonderful sheet is designed to fit oversized mattresses with an extra deep pocket. This set is more durable than both cotton and sateen fibers and has a soft feel. It is also fade-resistant and wrinkle-free with no need to iron. With extremely durable elastic around the entire bottom of the fitted sheet, it is sure to fit any mattress.