Andersen 837 Narroline Sash Balancer
Brand: Andersen
Match your windows (lower sash) visible glass size (width & height) to the chart
Works with Perma-Shield Narroline Double-Hung Windows manufactured from 1968 to Present.
Sash balancers are metal boxes that contain a nylon cord under tension.
The balancer number is a code for the tension and the cord length.
If you replace one balancer you should replace both balancers.