Channel balance (sash) replacement

A handy person from Quebec says:
I just want to be sure before I place my order...

The metal part of the sash measures 27". The stamping on the side is as shown 26-D-40. It appears to be a 351 series sash; however, I have no idea which option I should choose. I saw another poster post a similar question with a similar stamp and you asked what the weight of the sash was. After there were no responses.

So, is the weight of the sash necessary to determine which option to take? Is that the weight with the spring and plastic parts at the end or just the metal u-channel? How accurate would the weight need to be? I am not sure if I have a scale that would be that sensitive.

Let me know any other information that I could provide that may be of help. I will most likely order a dozen or more of these along with some handles that have pretty much disintegrated from sun exposure. Thanks.
User submitted photos of a window balance.
Profile picture of Tom
Tom from SWISCO responded:
Yes, knowing the weight of the sash is the best way to determine what option you need. If you have the S351-27, then you should see a weight rating chart under its pictures. This shows you what kind of weight each option can support.
Profile picture of Donna
Donna from SWISCO responded:
Also compare your balance to the Series 390, the difference from the Series 351 is the shoe depth.
Alternate view of 15-001
Series 390 has the 15-001 attached and
Series 351 has the 15-002 shoe attached
A home owner from Quebec says:
Do I weigh the sash with the spring loaded in it? I imagine these sashes must be within ounces of each other so I would need a scale that's pretty precise I imagine? Is it the spring that changes or the guage of steel for the sash that will change the weight of these things?
A home owner from Quebec says:
Ok, I think I am confused here. I assume you do not want me to weight this sash balance. I assume I want to weigh the actual window?
Profile picture of Tom
Tom from SWISCO responded:
Yes, the part of the window that slides up and down is known as a sash. We will need to know that weight.
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