For an extra-long twin-sized bed, the fitted sheet measures 39 inches in width and 80 inches in length and the flat sheet measures 66 inches in width and 102 inches in length. A comforter sold for an extra-long twin-size bed is 90 inches in length.
Although comforters specifically constructed for twin-XL beds exist, they are rare. Comforters for twin beds are 84 to 86 inches long, although twin mattresses measure 75 inches in length. Twin-XL mattresses measure 80 inches, and so a comforter for a twin bed would also fit a twin-XL bed. Most bedding companies market comforters as appropriate for both twin and twin-XL mattresses to eliminate confusion.