Coldwell 1/2 inch by 31 in length

With this combination of attachments, you could have either a S380-31 or S385-31 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 a 3040 spring strength option for your balance. 

Thank you and let us know if you have any other questions or concerns.

Comparison of the S378, S380 and S385 balance shoes.