A twin XL bed frame is designed to fit twin extra-long mattresses. Both twin XL and regular twin mattresses have a width of 38 inches, but a twin XL has a length of 80 inches, which is 5 inches ...

According to Kirsty Williams, VP of design at Serena & Lily, "daybeds and twin beds are generally the same size." Which means that in many cases, you can use them interchangeably!