19 inch rack (480 mm in metric) is a standard width of server racks used for rackmount computer and audio video equipment. The 19″ rack mount enclosure cabinet is the most common for mounting rackmount servers, RAID systems, switches, routers, audio video gear and more. 19″ racks are manufactured in many styles and depths for various conditions and equipment.Computer racks for 19″ rackmount electronic systems conform to standards established in the industry. 19″ rack standards are set by Electronic Industries Alliance (EIA), International Electrotechnical Commission (IEC) and Deutsches Institut fur Normung (DIN). 19″ racks use Rack Units (RU), which has been shortened to just “U”, for vertical height of the enclosure cabinets and equipment that goes inside. A U is equal to 1.75 inches, so 19 inch rack systems are described not in inch but in U’s of available space.For example, the XRackPro2 19” rack is produced in 25U, 12U, 6U and 4U sizes. The 19” rack that is 12U tall can hold up to 12U of equipment; so 12 units of 1U servers can be used or 6 units of 2U systems can be used or 4 units of 3U equipment and so on. That is the distance between mounting holes, the actually height of 19in equipment will be slightly less to make sure equipment will fit together.Filler panels for 19″ rack mount enclosures are used to fill in the empty gaps between equipment if space if left between. 19” rack filler panels for the XRackPro2 series are made in 5U, 3U, 2U and 1U sizes.Rackmount equipment goes inside a 19″ wide rack. 19″ rack mount servers, RAID systems, switches and more can be rackmounted. 19-inch racks can also hold audio video, medical, military and other rackmount equipment.