The U.S. laboratory module is long and wide. It is made from aluminum and stainless steel, and comprises three cylindrical sections and two endcones that contain the hatch openings through which astronauts enter and exit the module. The aft port of "Destiny" is connected to the forward port of Unity, and the forward port of "Destiny" is connected to the aft port of "Harmony". The ends are colored blue and white respectively for the crew to navigate easily. A -diameter window is located on one side of the center module segment.