A split-king is really two, extra-long twins pushed together. It is cheaper to buy two sets of these sheets just to use the fitted sheets and the pillowcases than it is to buy specialized sheets for this type bed. I gave the top/flat sheets to my daughter for her college XL twin bed. The sheets appear thin when held up to the light but they are soft and stay on the mattress even when the head and/or foot of the bed is elevated. I will most likely be purchasing two more sets in a different color.