Hello, this part is a plastic cap that sits on top of the window sash on each of the top corners. The cap engages with the spring, and helps to counterbalance the window.
These windows are from a new construction home built in 2003. The part is a plastic piece, it screws into the window sash with a single metal screw. I have a video that I uploaded to youtube that shows the window sash removed and one of the broken caps that need to be replaced, it can be seen here:
https://www.youtube.com/watch?v=5hW3_LF6HAg&feature=youtu.be
Spring and window dimensions are Spring: 30" height, 1/2" deep (or wide).
Window is 31"h x 46"w
Some markings on the spring say BSI 10, and 29_6
Thanks, hope that you can point me in the right direction with these parts.
PS, do you offer expedited shipping?