I didn't know either. But come 6 months from now, I probably won't again because the center bump buttons are nearly useless.
Who wants to go through every band and every source to get to the one you want. Or every station preset (even ones you never set).
There are too many buttons on that steering wheel.
TWENTY FIVE buttons !!!
Now if you could customize some of those buttons, that would be cool
Like Go Home on GPS and please don't ask me to confirm.