4U Roto shockmount rack case. Based on the ultimate strength series design, the Roto shockmount rack cases provide added protection for sensitive gear. With an internal frame mounted on adjustable elastomer shock absorbers on all eight corners, this revolutionary design controls the effects of shock and vibration on all three axes. The "sway" space around the internal frame provides natural air conditioning - very important for delicate equipment. They are less than half the weight of old fashioned wood racks.