How to decide sash balance Weight

Hello, thanks for writing in. I see that you were looking at the Series 380. I can't confirm if this is the right series without seeing the plastic attachments, but if you are confident that this is correct, then your stamp indicates that you would want the S380-26. With this series, the length is typically one digit higher than the stamp. If you go to the product page for S380-26, you'll see a stamp option for 2550, which indicates a sash weight between 25 and 28 pounds. This would be the one you would want. Please let me know if you have any further questions.

We typically don't recommend straying from the spring strength indicated by the stamp. If you're window is 26 pounds, then the 2550 option should work well for you. Choosing a lighter spring strength could result in the window not staying open.