Having some difficulty determining the right part to get

A home owner from Maryland says:
May 18, 2021
All,
I'm having a hard time figuring out which part I need. Most of the windows that I have are of the same dimension. I took out one sash and weighed it on a scale which came out at around 17.6 pounds. I located a stamp on the block and tackle which was 930. Measured the length which verified at 30" and the width at 9/16ths of an inch. I now see that 9/16" is 1/2", but don't see anything on the site for a comparable 930 channel balance. I'm probably missing something, but appreciate the assist.

Thanks!

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A home owner from Maryland says:
May 18, 2021
Added measurements of the shoes.
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Bob from SWISCO responded:
May 19, 2021

See either our S380-30 or S385-30. The difference between these two balances is the depth of the bottom nylon shoe, so compare both with your old hardware to see what matches best. See the image below. For the stamp option, I suspect your old balance's stamp is faded and once read 2930. Our stamp option of 2930 will support a window sash in the weight range of 16 through 23 pounds. 

Comparison of the S380 and S385 balance shoes.
Comparison of the S380 and S385 balance shoes.
30" Series 380 Channel Balance
30" Series 380 Channel Balance
S380-30
$11.30
30" Series 385 Channel Balance
30" Series 385 Channel Balance
S385-30
$11.30
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