A quick learner from Maryland says:
June 3, 2012
I need several replacement rubber bumper floataways for 40-plus-year-old metal bifold doors. We're remodeling to sell the house. The current bumper is 2 7/16" long with height of 1/2" and width across the top between 8/16" and 9/16". Will your 2 1/2" bumper work? The opening in the rail must be 6/16" since that's the measurement of the current bumper at the part that fits in the rail. But heck surely the size has shrunk over the last 4 decades. Thanks.
Paul from SWISCO responded:
June 8, 2012
Thanks for posting! It does appear that our 21-278 snugger is very similar to yours. I believe that it is the closest replacement part that we currently have. Just recheck your dimensions and see if you think it might match!