Coil spring balance replacements

A contractor from California says:
Hello I'm a contractor in California. I inspected a window today and pulled these out. Both casings the same size approx 4"x 1"
However the coil stamp pound indication was different. In one I pulled out a 4lb and 6lb coil. The other had both 5lb coils. The window that had the 4 and 6 lb coil wasn't holding the window up so I think it was replaced maybe with wrong coil. I'm not 100% sure but that's what i think. I need replacements if you have. ThNk you
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Bob from SWISCO responded:

Thanks for posting. This looks like the 15-102 Double Side Carrier, which uses Series 145 Coil Balances. Also see the 15-108 Sash Cam, 15-222 Guide Base, and 15-223 Guide Cover.

As far as the window not staying up, the best thing to do is to weigh the window sash. Having 4lb and 6 lb springs on one side is actually equal to having (2) 5 lb springs on the other side; however, it is possible this simply isn't enough overall support for the window weight. Let us know what that exact weight is, and we can narrow down what you need. 

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