: The "E" revision, released in December 2005, is the most recent update, following the widely known EIA-310-D.
While often called the "19-inch rack," this refers to the front panel width of the equipment; the actual internal mounting rail opening is typically around 17.75 inches . Eia Eca-310-e Pdf
"You know," Elias said, pointing to the rails, "the only thing that’s actually 19 inches is the front panel. The actual opening is just over 17.7 inches". : The "E" revision, released in December 2005,