Window coil balance

Thanks for writing in, and thanks for your patience during this busy season. This looks like a Series 180 Coil Balance. A stamp of '4' on the spring itself likely indicates that it's an S180-4, which can support 4 lbs of weight individually. If you want to be sure of the weights you need for all your coil springs, the best thing to do is to weigh your window sash. Give us that exact weight, and we can work out what you need. Many thanks.