The maximum display resolution supported when using the TBT-6950PD’s HDMI video outputs is 3840x2160, and the maximum refresh rate supported is 60Hz.  

Resolutions higher than 3840x2160 and refresh rates higher than 60Hz are not supported.

The maximum resolution and refresh supported when displays are connected to the dock’s downstream Thunderbolt ports using a USB Type-C cable or USB Type-C video adapter will vary and depend on the capabilities of the USB Type-C video adapter, the host system, and the number of displays connected.