4U Roto Rolling Rack We've completely overhauled our 4U, 6U, and 8U Roto Rolling Racks, incorporating an innovative new design that includes our new one-touch pull handle and back lid mounted wheels for easy transport. We've also updated the exteriors so new Roto Rolling Racks will easily stack with our existing standard and shallow racks. Four military grade butterfly latches secure each lid with an internal rubber gasket that keeps water out so sensitive electronics stay safe and secure in transport.