Window balance 16-4 GE5 CMC 75

Hi, Mark. Try the 17" version of the same balance. If your metal bar (not the whole thing) is 17", this is correct. The 17" balances will have "1640" options, similar to what you have.

That sounds like you might have something special. Can you show me one photo of the top nylon attachment and one photo of the bottom nylon attachment? I would also like a photo of the metal clip at the end of the cord. I'm pretty sure I know what you need, but I wanted to be 100% sure. Photos will confirm. I would also like to know how many you need.

These pictures are perfect, thank you! This isn't a special type of balance like I was expecting, though. If I didn't have any other information, I'd say this looks like just a regular S385-17. For the option, I'd go with 1640.

But you say the metal channel is 17-3/4" long. That's pretty weird for the hardware I see in your pictures. I can't think of any reason why the manufacturer would stamp an 18" long balance with "16-4." 

If you are confident that that's how long your metal channel is, then you may be able to get our S385-18 to work. To determine the proper option, I would recommend weighing your sash on a scale and referring to the chart on the S385-18 store page to confirm which option would be best. They all start with "17" for the first two digits but that doesn't matter. What's important is sash weight.