That's a factory mirror I think Bill, at least mine has them on it and did when I bought it 12yrs ago. I guess the first owner could have put them on too as all he did with it was pull a trailer too(he had horses, my horses are under the hood

 

I wondered about those being factory. Tyler was telling me he met a guy that had the twin truck to his and that guy had these same exact extenders on his mirrors. I looked at mine and they're made by Extend-a-mirror. I know the mirror is factory, but are the sliders factory too?

 

Her they are.....Extend-A-Mirror

 

I really couldn't say for sure but I thought they were. Like I said the po may have put the extenders on, not sure. I had to buy a couple new plastic extender pieces as mine were cracked. They are kind of cheesy, mine don't stay tight very well. Means I leave them extended all the way out all the time, I've been contemplating red loctite on them, that would fix the coming loose.

 

If you leave them out all the time that would work.