Racks feature three shelves “ two of which are heavy duty for kegs and the third (usually on top) is for general storage. Heavy duty shelves: Rectangular frame of 1 1/2″ x 2 3/4″ x 0.07″ wall extruded aluminum square tube, with 1 1/4″ x 2 1/4″ x 0.100″ T-bars welded inside perpendicular to shelf length. 3″ spacing between T-bars. Top general storage shelf: Rectangular frame of 1 1/2″ x 1 3/4″ x 0.07″ wall extruded aluminum square tube, with 1 1/4″ x 2 1/4″ x 0.10″ T-bars welded inside. 3″ spacing between T-bars. Shelves are adjustable in 2″ increments. Each shelf corner has a welded-in-place heavy duty extruded aluminum collar with set screw. Posts are 1 5/16″ diameter, marked in 2″ increments, and include end cap on each end. Shipped knocked down, and assembles easily with allen wrench provided.