Balance replacement

Thanks for posting. This looks like either an S351-28 or S390-28. The only difference between these two balances is the 'depth' of the bottom nylon shoe, or the 'heel-to-toe' measurement. See the diagram below for reference. Compare both balances with your old hardware to see what matches best.

Comparison of the S351 and S390 balance shoes.

You also have to choose a stamp option, which designates the strength of the balance. A channel balance should really only have one stamp: 27A would correspond to our stamp option of 2710, whereas 27B would match with 2720. If in doubt, weigh the window sash. Give us that exact weight and we can work it out for you.