18 inch spring sash balance

18B B.S.I HP
1/2" x 1/2" x 18" One philips head screw holds in vinyl channel
Window size is 31 1/4" wide, 19 1/2" high, double pane insulated vinyl window.

Cable seems to have bound up, slipped off guides. Looking for replacement. I recently ordered other parts for this type of window under order number 1501673. Thanks for your help in finding this part!