Channel balance tension specification

A quick learner from Boulder Creek, California says:
I believe I've identified the correct part but don't know what tension option to order.

The window is a Milgard.

The photo shows the only markings on the old balances that I could find. One has 'AS' and the other 'BS' although they look identical in design.
Thumbnail of the uploaded file named IMG_20210226_152232.jpg
Thumbnail of the uploaded file named IMG_20210226_152249.jpg
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Tom from SWISCO responded:

Thanks for your photos. Based on what I see here, you have either our S380-21 or S385-21, depending on the depth of the bottom shoe. That's the only difference between them. I recommend measuring your shoe and referring to our dimensions to confirm the best match.

Comparison of the S380 and S385 balance shoes.
Comparison of the S380 and S385 balance shoes.
A quick learner from Boulder Creek, California says:
Yes, I believe they are S385. Thanks.

My question was about the option# but I've since been able to weight the sash and it comes to 22-23 lbs so I've chosen option 2040. I hope that's right as I've placed the order.

Comment: Your web site is among the best retail web site I've seen! Extremely well designed and engineered. Developers and designer should be congratulated. Much appreciated.
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Tom from SWISCO responded:

You're very kind to say so! That means to much to hear. We definitely try our best to stand out, in terms of quality.

As for your stamp option, you are correct. If your sash weight is a little under 23 pounds then 2040 should be perfect. Sorry for misunderstanding the original question of your post.

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