What does "2U" mean in a 2U rack-mount chassis? What is the difference between 1U, 2U, 3U and 4U?
This is my latest article, hope you like it: https://www.utmel.com/blog/categories/integrated%20circuit/what-is-serdes

it's the number of standard 19" rack mount vertical units the rack has

1u = 1.75"

eurorack modules are 3u

those tile things are 1u

buchla and serge etc are 4u

moog are 5u

Utility modules are the inexpensive, dull polish that makes the expensive, shiny modules actually shine!!!