Window channel part questions

A quick learner from USA says:
I was doing good navigating your website on how to choose a window channnel until I got to the last page. It asked what option i need, i.e. B,C,D ? Not sure what you mean by that.
Product Code: S775-18 is what i need as i followed your layout. Shoe size 1.25"
Can you tell me which option B, C, D I need based on my photo attachments? There are 12 photos.
User submitted photos of a window balance.
Profile picture of Paul
Paul from SWISCO responded:
The option indicates spring strength. You can usually use the stamp printed on your metal channel as reference, but yours appears to be different than any of the options we have. That probably means your balance was just made by a different manufacturer. I recommend weighing your sash on a scale and referring to the chart shown on the S775-18 store page, that will tell you what will work best.
How to install a S775 balance
How to install a S775 balance
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