The Cisco 7200 Rack Density System (RDS) is a sheet-metal assembly used to organize Cisco 7206 VXR routers vertically into a rack. The main function of the RDS is to change the airflow from side-to-side to front-to-back. When routers are mounted horizontally in a rack, air flows sideways between the racks. Vertical mounting of routers prevents overheating in the last rack in a series of racks.The RDS is suitable for most EIA or ETSI 19-inch, seven-foot high or six-foot high, four-post racks. You can purchase optional rack-mounting brackets for wider racks. The RDS mounts in the rack in any one of eight configurations, depending on front orientation or reverse orientation. Up to three RDSs can be mounted in most typical seven foot equipment racks with at least 40 usable rack units (RUs) for EIA racks, or 69 usable RUs for ETSI racks. Each RDS accommodates up to three Cisco 7206 VXR routers and/or filler panels, mounted vertically.