MW Twinseal replacement window balance

A quick learner from Norwalk, CT says:

I'm trying to get some replacment balances for a customer of ours. It's for the MW Twinseal Vinyl unit (from 1999). I have attached pics. Your 850 series looks like the part, except the top is different. Can you let me know if your will still work?
User submitted photos of a window balance.
Profile picture of Paul
Paul from SWISCO responded:
I agree, this appears to match our Series 850 crossbow balance. It's not made with that top hook anymore, ours just screws in. You will need our 26-200 screw plug. This actually inserts in the slot that accepted your old hook. You would then simply screw the Series 850 balance to the 26-200 plug.
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