30" window balance for Lawson

Hello, thank you for posting,

With this combination of attachments, you could have either an 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. 

When measuring the length, only measure the metal channel excluding the nylon attachments. Since there is no stampings that usually determine the strength of the spring needed, you will need to weigh the window sash. Once on the product page for the correct series and length, compare to the strength chart to choose the correct stamp option.

Let me know if you have any additional questions! 

Comparison of the S378, S380 and S385 balance shoes.