I have these parts three different sizes. 1440, 2040 , 2020
Thanks for posting. These are called channel balances. They are spring mechanisms that regulate the window's movement. I am sure we can help replace these, but those stamps are not identifiers. They just tell us the strength of the balances. For each 'set' of balances (1440, 2040 and 2020), we need to see the nylon attachments at both ends of the metal channel. The style of attachments will determine the replacements you need. We will do our best to help from there.
Thanks for getting these photos to me. Assuming the nylon attachments are the same for all the sets of balances you have, this is either a Series 351 or Series 390 Channel Balance. The only difference between these two balance series is the 'depth' of the bottom nylon shoe, or the heel-to-toe measurement. See the diagram below for reference. Compare both balances with your old hardware to see what matches best.
For the 15" length balances, you'll need either the S351-15 or S390-15, with a stamp option of 1440.
For the 21" balances, choose either the S351-21 or S390-21, with stamps of 2020 and 2040, respectively. let me know if you have further questions.
