Sash window balance springs

Question

These are from one of my windows and they are 40 years old and getting creaky. What would the replacement be?

Bob · Accepted Answer

Thanks for posting. It looks like you have either Series 351 or Series 390 Channel Balance. The only difference between these two balances is the 'depth' of the bottom nylon shoe. See below. Measure your old balance's shoe depth to see what matches best. Let us know if you have questions regarding choosing the length or stamp option.

Comparison of the S351 and S390 balance shoes.