Window coil balancers

Thanks for posting. This looks like our 15-087 Pivot Shoe, which can be stacked with our 15-086 Tandem Housing. This Pivot Shoe and Housing works with our Series 180 Coil Springs. To know what spring weights you need, remove your old coil springs from the shoe and housing and search for stamped numbers. These should indicate the spring weights you need. If your coil springs are missing stamp numbers, weigh your window sash. Let us know that precise weight, and we'll figure out what you need.

Is the first number in each of these stamps by any chance printed larger or more pronounced than the other digits? Either way, while I can't be certain, I suspect that the first number in each of these stamps represent the spring weight you need, while the last two numbers simply refer to the 'travel length' of the coil springs, which you needn't worry about. If my assumption is correct, then you need the S180-4 and the S180-5 on both sides of your window sash. This also would indicate that your window sash weighs 18 lbs, since you have 9 lbs of support on either side of the sash. I'm not 100% sure though, so if you want to be safe, it would be best to weigh your sash to confirm this.