18 springs and 18 slides

Can you confirm the diameter of the outer tube? Based on the style of your balance, it should be either 3/8" or 5/8". I'd wager yours is 5/8". If so, I recommend our S600-24. 

Please note that our tubes are made of metal, not plastic. Our balances will also have a red tip instead of a white tip, but will work fine for your windows. Finally, our 75-006 charging tool should be helpful for installation. 

I'm not sure about that pivot shoe. I think yours is discontinued, so we'll need to see if we can find a modern replacement. Can you remove it from the window and give me its exact thickness? I cannot tell what it is from just a tape measure. Can you also show me a photo of the pivot bar that interacts with it?