Coil balance

It looks like you have our 15-180 pivot shoe and 15-186 clip. The spring is likely a match for our Series 190, but without a stamp you'll need to get the exact weight of your sash and then divide that by however many springs are supporting it. 

For example, if your sash weighs 24 pounds and it's supported by 4 springs, you want our S190-640 spring, since these carry 6 pounds each. 

If you aren't sure what spring to use, just tell me the weight of your sash and how many springs are used to support it and we'll do the math for you.