Tail shaft seal and yoke quetsion

Hey guys. I gotta question on one of my weak points. This picture below is a tailshaft to a 727. In my hand is a seal that I think goes onn or in I should say to the tailshaft. The yoke of course slips in and is covered by the dust boot.

Notice theres something of a seal in the tailshaft allready.

Do I need to put that thing in my hand in?

Or can I run without it and be OK.

The inside diameter of the seal in the tailshaft is the same as the one in my hand. I like the dust boot cover and normaly see it this way.

Do I need to remove one for the other?

The one in there now has a lip that sits on the houseing, like it belongs there.