Replace single hung balance spring

Question

Hello,
I'm looking for a pair of replacement balance springs for a single hung window.
The channel is 5/8", 22 inch length, and stamp 21-5.
There's a name on the part called "21 5 DP Caldwell"
Can you tell me which part to order?
Thank you,

Casey · Accepted Answer

Hello,

With this combination of attachments, you could have either the S378, S380, or S385 channel balance. You’ll need to measure as shown below. The Series 380 has a 1" bottom attachment, and the Series 385 has a 1-3/32" attachment.

You'll also need 2150 spring strength options for your replacement balances. Thank you, and let us know if you have any other questions or concerns.

Comparison of the S378, S380 and S385 balance shoes.