A quick learner says:
November 3, 2013
Window won't stay up. Balance springs are working because when I unscrewed the balance spring it sprung down. These stoppers keep falling and won't hold the window up.
Paul from SWISCO responded:
November 5, 2013
This is what's known as a pivot shoe. Yours in particular resembles our 15-177. Carefully compare its dimensions to your hardware and see how they match up.