Coil or constant force balance

Hello! Balance stamps are usually rated in sequential order, so a stamp of "F" typically corresponds to 6 pounds. However the best way to confirm is to weigh your sash on a scale and divide that by how many springs support it. So for example, if your sash is 20 pounds and you have 2 springs per side, you'd want the 5 pound option.

Any common bathroom scale will suffice.