Our finest cotton sheets are exceptionally soft and durable, made from responsibly sourced 100% Supima cotton for long lasting comfort. Pillowcases included. Supima cotton is a rare, superior type of cotton grown in the USA. It represents less than 1% of the cotton grown worldwide. Its extra-long staple fibers are strong and soft with excellent color retention. They resist pilling, breaking and tearing, for incredible resilience and long-lasting quality. ExactFit™ sheet design allows our sheets to stretch and move with our unique smart beds as they flex, and recover between uses, for a smooth, perfect fit. With our SmartFit™ design, sheets stay secure all night. A fully elasticized edge, elastic corner seams and anchor bands keep fitted sheets in place. Logic™ Labels on Sleep Number® bedding make it easy to see which way your bedding fits, right from the start. Simply align the labels at the bottom right corner for easy bed-making. These supima cotton sheets have a 600 thread count for lightweight softness and breathability. Our sheets are designed to fit any mattress up to 15" mattress thickness. Includes:One oversized flat sheetOne fitted sheet (Split King and Split California King sets contain two Twin Long fitted sheets)Two pillowcases (Twin and Twin Long include one pillowcase) Learn more about how to find the right sheet or watch our how-to videos.