The number you're referring to only indicates the spring strength on the balance and does not help with the identification of the balance. If you have not done so already, you will need to remove the balance completely out of the window. From there, send us some photos showing the complete balance including the nylon fittings on both sides. This will help us determine which balance can work for your windows.
Thanks for your photos. Your balance looks close to both our S380-29 and S385-29. The difference between these two is the depth measurement of the bottom balance shoe. For the Series 380, the depth of the bottom shoe measures 1" and for the Series 385, it's 1-3/32". Measure the depth of your bottom balance shoe, like in the diagram below, to determine which balance would make the best match. Whichever one chosen will go with the 2830 option.
Ok, great. If your depth measures 1", then you can go with the Series 380 balance that we mentioned in our previous reply.
