I stumbled on this on a Ranger foroum I'm on, and installed one in my Ranger yesterday. What it does, is when you switch on your highbeams, it allows you to still have the low beams on, along with switching on the fogs if you have them as well.
It all started when I felt the need for a little extra vision when driving to work in the dark each morning. I live knee deep in deer country, along with the occasional bear, and sometimes an elk. Luckily, with the deer attacks I've had, no real damage has been done, but, it's not if, it's when, I finally end up wrecking something.
You can simulate the effect by pulling on your flash to pass, except for the fogs.
I only have this on the Ranger for now, but one is in the future for the 150 as well.Brite Box - Truck Customizers

 

Cool, daddy like !