The inner opening width between the rack rails must be at least 17.75 inches (450.8 mm) to allow the chassis body to slide into the rack. 3. Mounting Hole Types
While the is the go-to, you may also need: Eia Eca-310-e Pdf
Predominant in modern enterprise IT and data center environments. They utilize removable cage nuts , which protect the rail threads from stripping and allow easy swapping between different thread sizes (M6, 10-32, or 12-24). The inner opening width between the rack rails
from the bottom hole of one RU to the top hole of the next RU. Eia Eca-310-e Pdf