Frame and supports: 1″ square aluminum tubing. Six cross supports. Tray slides: extruded aluminum angle 1 7/16″ high x 1 7/8″ wide x 1/16″ thick bearing surface with raised beads providing a minimum of friction. Slides are riveted to frame 3″ apart. Casters: 5″ diameter non-marking swivel stem casters with polymer tread. Shipped assembled.