what's this button for?
 

Hi, in my 06 f250 behind the rear view mirror there is a small black box with a button on top of it. anyone know what the box and button is for? it seems to be a factory componant. thanks for any and all help

Some had a compass that displayed in the mirror and some had an auto dimming feature within the mirror to help when vehicles approached from the rear with their hi beams on. Owner's manual should explain if factory installed.