Vinyl window part
A quick learner from Saginaw, MI says:
April 13, 2015
There is one of these on each side of the window track. The plastic covering is breaking apart and there is a circular spring inside it.
Paul from SWISCO responded:
April 14, 2015
If your coils are 3/8" wide, and if you have two of them behind the covering, you could consider our 15-204 support.