I have to replace some balancers on some Marvin Windows.

Thanks for posting! I am confident we can provide you with a replacement for the balance you have here. Although, there are a few details I'll need to see to make the correct recommendation.

Please provide a photo of the bottom attachment from the balance. It is important to see the shoe to ensure that they are assembled with the correct parts. I'll also need to see a photo of the bracket in the center of the balance, this is where the spring and the string meet in the middle.

Feel free to reach out with any questions you might have.