29"window balance no tilt

Hello there. Can you confirm the metal channel, not including the nylon attachments, is 29" long? Can you also show us any stamp on the metal channel, if there is one? We should be able to narrow this down from there.

Thanks for getting back to me. This is either a S378-29, S380-29, or S385-29. The only difference between these three balances is the 'depth' of the bottom nylon shoe. See below. Measure your old balance's shoe depth to see what matches best.

Comparison of the S378, S380 and S385 balance shoes.

You then have to choose a stamp option, which reflects the strength of the balance. Since your old balance has no stamp printed on it, weigh the window sash these balances support. You can use that weight to choose the right stamp option.