Almost all networking cabinets follow the EIA-310 standard, which specifies a 19-inch internal mounting width. This universal standard ensures that equipment from any manufacturer will fit properly in your cabinet. Therefore, you don't need to worry about compatibility issues when buying from. Common server rack sizes are 19‑inch width, heights like 42U or 48U, and depths from ~24″ to 48″. Most IT environments default to 42U, 19-inch width, and 1000–1200 mm depth unless space constraints or special equipment dictate. One U equals exactly 1. 45 millimeters, if you prefer metric). Options include 24″, 36″, 42″, 48″, and 59″.