Window balance forhome

Thanks for posting. Assuming the metal track, but not including the nylon attachments, is 31", then this is either a S351-31 or S390-31 Channel Balance, depending on the depth of the nylon shoe. See below. For a stamp option, look for an old stamp that indicates this on the metal channel. If there is none, you can weigh the window sash and use that exact weight to determine it. Let me know if you have further questions.

Comparison of the S351 and S390 balance shoes.