Window counter balance

Thanks for your post! The nylon housing you have can be replaced with the 15-087 Coil Housing Pivot. This is compatible with the Series 180 Coil Balance, anchored to the window using the 16-024 Mounting Bracket. 

Since your housing is stamped with a 6, you'll likely need the S180-06. One 6lb coil on each side of the window will support a sash weighing around 11 to 13lbs.

Detail of 15-087