A "twin XL" mattress is a specific size of mattress that measures 38 inches wide by 80 inches long. It is five inches longer than a standard twin mattress, which is 75 inches long. This extra length makes it a popular choice for taller individuals and is commonly used in college dorm rooms. The twin XL size is often paired with twin XL bed frames and bedding, making it easy to find compatible accessories. Many universities provide twin XL beds in their dormitories to accommodate students, ensuring comfort for those who may need more legroom while sleeping.