This part stops the sliding shower door from over extending to one side and having the wheels come off the track. This is a curved corner shower. These parts are in the the center of the top track and contact the wheels as a bump stop.
Bob from SWISCO responded:
August 19, 2020
I am afraid I'm not familiar with this type of door bumper. Could you use something like the 10-111 instead? Take a look and see what you think.