Balance question

Well, that's actually a somewhat complex question. The stamp represents the strength of the spring, but this can often lighten the strain on the string. Every component in a balance works closely together. They're precise systems. However, it's important to keep in mind that it is possible to have a balance that is too strong. I highly recommend weighing your sash on a scale and referring to the chart on the S350-28 store page. That will tell you exactly what you need. I would not go heavier. The average lifespan of this kind of balance is around 5-10 years, depending on how often the window is used.