Balance from a Tri-Built CuttingEdge double hung windo

A quick learner from New Jersey says:
Do you have this part?
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Bob from SWISCO responded:

Hi there. This looks like a 15-181 Support Detent Clip. This clip is used with Series 190 Coil Balances. You may wish to make sure your pivot shoe looks like our 15-180 to confirm this, as the identity of the pivot shoe confirms the identity of the coil balance system. Look for stamp numbers on your coil springs to confirm what spring weights you need. If there are no stamp numbers, weigh your window sash. Give us the exact weight of the window sash and we will figure out what you need. Many thanks.

A quick learner from New Jersey says:
Yes, the pivot shoe does match the 15-180. There is no stamp on the coil - the window sash weight is 12.5 lbs. Thanks for your help.
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Bob from SWISCO responded:

Thanks for getting back to me. If the sash weighs 12.5 lbs, then I think you could get away using a S190-640 6 lb coil spring on both sides of the sash, for 12 lbs of total support; being a half-a-pound off shouldn't affect window function. This also means you could use the 15-186 single coil clips for support. 

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