The 1SKB-R1906 was designed to add expandability to the new 1SKB-R104 and 1SKB-R106, as well as the 1SKB19-R1006(V) and the 1SKB19-R1010(V). The 1SKB-R1906 can even stack on itself (remove the casters from the top one before stacking). The Roto Rack Expander case features 6U on the front and 6U in the rear with front and rear covers with SKB's glass reinforced TSA trigger release latches. Heavy-duty locking 5 inch casters make for easy transport and durable nylon straps secure the gear together. There is a 1" border around the top of the case (to help hold whatever is on top, in place). So the actual depth (height) is 16" and if you include the wheels, it's 21" (20" from the bottom of the wheels to the top mounting surface)