Sash Weights for Spiral Bals

The current balances are blue, not red.
I'm looking at series 600.



Thanks for reaching out to us. This is a fairly common question, and a reasonable assumption; however, that's not quite how these work. The S600-34 black tip will not last longer for your 28 pound window. On the contrary, its performance will actually be worse.
Because you have more weight pulling up on the sash (from the balance) than there is pushing down (from the weight of the sash itself), then the window will become much harder to close. With that kind of difference you may even find that the window drifts up on its own.
When it comes to these parts, think of it like Goldilock's porridge. Not too weak, not too strong. You want it to be just right. Remember that the key word here is "balance."