window balance and parts replacement

Hello!

It appears you have our S351-25 or S390-25 channel balance. The important difference between these two parts is the bottom shoe size. Our Series 351 comes attached with a 1" deep shoe, and the Series 390 comes attached with a 1-1/8" deep shoe. Measure as shown in the image below to determine the best match. You will also need the 2420 strength option for a sash weighing 9 to 15 pounds. 

Comparison of the S351 and S390 balance shoes.