Flipping Normal map for symmetrical objects

I saw a normal map here, that was only for half of a symmetrical object, which lead me to make this.

The UVs (I just made a plane for this) are mirrored across the U axis, as seen in the bottom of the image.
Or just multiply the normal map by -1,1,1. Not sure why I felt the need to use Appends.

Note: The red channel is being flipped because the mesh is vertically symmetrical.