non-tilt block and tackle

A quick learner from Maryland says:
I need two replacement block and tackle balances. see attached pictures. 21" length metal to metal. 5/8" depth. I think the stamp is 2040 on the side. any advice of how to order?
User submitted photos of a window balance.
Profile picture of Paul
Paul from SWISCO responded:
Looking at your nylon attachments, I would recommend our S350-21 channel balance. I would also recommend a 2040 option. Check it out and see what you think. All orders can be placed directly on our site.
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