This thing is a new modified case for the GTeng T909 FPV Watch (probably also sold under different brand names). It only replaces the bottom half shell, you still need the original top case, buttons and screws. The stock linear antenna is replaced with an SMA connector to allow using a better antenna, reception has been improved greatly with this! See the last attached picture for a reminder on how to attach the battery and antenna cables.
Also included is mounting hardware to add the display to an RC transmitter like my FlySky clone.
All parts have been created with OpenSCAD and can be customized easily.