• 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.
• The proper balancer must be used to maintain the lower and upper sash in an open position.
• If you replace one balancer you should replace both balancers.

Note: For instructions on how to replace balancers view the (Size Guide & Instructions) section.