Andersen Window - Perma-Shield Narroline Counter Balancer, # 331Can be used to Replace: 319, 325Note: Jamb liners may also need to be re-ordered.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.Related Andersen Window Parts:1626018 - Balancer number 431 - used to replace 419, 425, 4311626024 - Balancer number 531 - used to replace 519, 525, 5311626029 - Balancer number 637 - used to replace 623, 627, 6311626034 - Balancer number 737 - used to replace 725, 727, 7311626037 - Balancer number 837 - used to replace 823, 827, 8311626043 - Balancer number 939 - used to replace 927, 931, 9371626044 - Balancer number 1033 - used to replace 1027, 10311626045 - Balancer number 1131 - used to replace 1131