This is the largest metal roller that goes on the ledge that is about chest high and under a cover on the side of your VW Bus. It allows the door to roll smoothly open and closed. If this roller is bad the door will not work properly.
Rear Hatch Window Seal for 64-79 VW Bus
Vent Wing Seal for 68-79 Bus (left)
Nylon guide block for middle hinge of sliding door for 63-79 VW Bus
Front Door window Regulator (right) for 68-79 Bus
Front Door to Body Seal (right) for 68-79 Bus