How do I know what series balance this is?

Hello,

With this combination of attachments, you could have either the S380-17 or S385-17 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 1620 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.

Using the incorrect balance can cause long-term issues, so we always suggest installing exact replacements. As long as your balance shoe measures over 1" deep, you should be good to go with the S385-17 (1620) balances.