This is the rubber that goes into the bracket of the bottom of the center of the door, for 1969-1970 Mercury Cougar and Ford Mustang glued-in door glass. See D0ZZ-6521762-A for the 1969 glued-in door glass. Note that this bumper substantially shorter than the 70 version. If you bolt a 69 door on a 70 or a 70 door on a 69 don't forget to change this part or your door glass height when all the way down will be off.
Ford part # C9ZZ-6521762-A.
Do you have questions about Glue-In vs Bolt-In glass? How about how to properly install Glue-In glass in your 1969 Cougar or Mustang? Check out our video below for some great glassy information!