Window balancers

Hello there. The metal channel looks to actually be 20" long, which would make sense with that 19-5 stamp (the length on these non-tilt window channel balances is usually 1" greater than the first two digits of the stamp). Based on the attachments, you have either an S380-20 or S385-20. The difference between these two channel balances is the depth of the bottom nylon shoe, or its measurement from 'heel' to 'toe'. See the illustration below as a reference. Measure the depth of your old balance's shoe to determine which replacement matches best. In either case, for a new stamp option go with 1950. Let me know if you have any other questions.

Comparison of the S380 and S385 balance shoes.