The USB 3.0 Docking Stations and adapters can output 4K (3840×2160) resolution but only at 30Hz. This is important as some displays only accept 3840×2160 60Hz signal.
If you have a 4K display and want to pair it up with a Docking Station or USB Graphics adapter you need to make sure that you meet this specification.
These cover the DisplayLink DL-5500, DL-5700 & DL 5900 chipsets.
Here is a screenshot of the DisplayLink Manager configured at 4K