The Mobile Pixels external monitor attaches to the back of your ... side of your primary screen or prop it as a stand while in portrait mode. This laptop screen extender also has auto-rotation ...

As a result, I took my second monitor and mounted it in portrait mode, and to be honest, I don't think I could ever go back.

A computer monitor that is taller than it is wide. Most portrait monitors are actually landscape monitors that can be swiveled into a portrait orientation. See landscape monitor and portrait.