This SmartRack 48U Standard-Depth 4-Post Premium Open Frame Rack is an expansion model with no sides, doors or roof. An expansion model is useful when baying together multiple enclosures. Its integrated baying tabs make it easy to combine multiple enclosures in rows for data center applications. The SR48UBEXPNDNR3 houses 3,500 lb (1588 kg) of standard 19" rack equipment in 48U. The front and rear pairs of vertical rails have square mounting holes that are adjustable in quarter-inches increments from 4 to 37". Adjustment is quick and an easy-view depth index ensures consistent rail placement without requiring time-consuming measurements. Each rack space within the enclosure is numbered for ready reference and supports tool-less button-mount 0U installation of up to four compatible PDUs and cable managers. All components of the SR48UBEXPNDNR3 are grounded to the enclosure frame. Front and rear threaded grounding points are provided for connection to the facility earth ground. To simplify deployment, the SR48UBEXPNDNR3 comes with heavy-duty 3" preinstalled casters that enable it to be easily maneuvered into the desired location, where it can be secured by adjusting the preinstalled levelers. Note: The casters are intended for minor position adjustments and are not designed for moving the enclosure over long distances.