Interior sealing strip for rear door glass
This is the interior horizontal furry seal that attaches to the rear door and seals against the window glass to stop draughts.
Length is 810mm and is listed for cars made after May 1965. Before then the seal strip was 797mm long, so this should be able to be adapted for the earlier cars.
We often see these fitted to cars upside down. Please note that the lip / ledge on the seal goes at the bottom and tucks under the metal part of the door. Yes, they are a bit awkward to fit, but that's a Citroen for you! Fit this before the outer seal.