One RMU is equal to what measurement?

The correct measurement for one RMU (Rack Management Unit) is 45 mm, which is equivalent to 1.75 inches. This standard measurement is commonly used in telecommunications and data center environments to help define how equipment is mounted within a rack. The RMU provides a consistent way to measure the vertical space that equipment occupies in server racks or cabinets, ensuring that different components can be mounted efficiently and systematically.

In the context of data center design and equipment installation, being familiar with RMU measurements is vital for planning and optimizing space, as it helps technicians and engineers determine how many devices can be installed within a given rack height. The other options do not align with the standard definition of an RMU, as they represent different sizes that are not used within this specific context.