Aluminum sash lifter

Thanks for your photos. Based on what I see here, you have either our S380-30 or S385-30, depending on the depth of the bottom shoe. That's the only difference between them. I recommend measuring your shoe and referring to our dimensions to confirm the best match.

I also note that your stamp reads 29-9. That "-9" suffix is different from how our balances are rated. You will need to get your precise sash weight in order to determine the proper option for one of the two balances mentioned above. We have a weight chart on each store page that you can use as a reference for picking the best one.

Comparison of the S378, S380 and S385 balance shoes.

Great, thank you. That would make it the S380-30. For a 20 pound sash, I'd suggest the 2930 option; as you can see on our store page, that option carries 16 through 23 pounds.