Highrise™ LTH Twin Xl The durable, extra tall Highrise™ LTH bed foundation creates up to 60 cubic feet of storage space and saves money by eliminating the need for a box spring. Simple to set up, the frame features an extra durable, welded support brace to ensure a quiet, solid foundation. L : 37.5 - W : 4 - H : 39.5 - W : 31