What does the U mean in shipping container prefixes?

The "U" in shipping container prefixes doesn't stand for anything specific. It's simply a placeholder character used to distinguish different container types.

Here's how it works:

* The first letter: This indicates the container type (e.g., U for a dry cargo container, R for a refrigerated container, etc.).

* The second letter: This is a placeholder, and it can be any letter. It's not a specific designation.

Therefore, "U" in a container prefix like "UCSU" simply indicates a standard dry cargo container. The "CSU" part is the code for the container's size and other features.

Here's an example:

* UCSU: "U" indicates a dry cargo container. "CSU" indicates a 20-foot standard container.

In summary:

The "U" in shipping container prefixes is not a specific designation, but a placeholder character for a dry cargo container. It helps differentiate it from other container types.