All-welded construction. Both racks are constructed of high-strength aluminum sections. Frame and supports: square aluminum tubing. Crossbraced front-to-back and side-to-side on top and bottom of unit. Rack slides made from aluminum angles, secured to frame at a slight angle for gravity feed. Casters on mobile unit: 4″ diameter non-marking swivel plate casters with polymer tread, two with brake. Stationary unit comes with adjustable feet. Provides automatic stock rotation when loaded from rear. Shipped assembled.