Replacing two (2) window balance channels

Question

The balance channel has the numbers 2740 imprinted vertically on the back of the channel. Then BS1 or BSI below the zero of the numbers imprinted horizontally.  The channel is 28 inches long and 1/2 inch wide.  Let me know if you need more photos.  Thank you!!  Julia Harding

Bob · Accepted Answer

Hi Julia. This looks like either an S351-28 or S390-28. The only difference between these two channel balances is the depth of the bottom nylon shoe, or the measurement from 'heel' to 'toe'. See the illustration below for reference. Compare both with your old balance to see which matches best. Make sure you use the balance that has an undamaged shoe to measure this. In either case, choose 2740 as a stamp option. Let us know if you have further questions.

Comparison of the S351 and S390 balance shoes.