Andersen 431 Narroline Sash Balance

Andersen Perma-Shield Narroline sash balancer 431. 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. The proper balancer must be used to maintain either the lower sash or the upper sash in an open position. If you replace one balancer you should replace both balancers.