Rack-mounted units are devices designed to fit into standard 19-inch racks, which are commonly used in data centers and server rooms. These units can include various types of equipment, such as servers, network switches, and storage devices. By organizing equipment in a rack, businesses can save space, improve airflow, and simplify maintenance. These units typically come in a specific height measured in rack units (U), where one rack unit is 1.75 inches tall. This standardization allows for easy stacking and installation, making it convenient for IT professionals to manage and upgrade their systems efficiently.