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Emily from SWISCO responded:
August 6, 2021
Hello there! It looks like you have either our S351, with a 15-002 bottom attachment, or S390, with a 15-001 bottom attachment. Take a look at the image below to determine which balance you'll need. Can you also double check the length on your metal channel for us? Is there a stamp on your metal channel? If not, you'll need to remove and weigh your sash to choose the appropriate spring strength option. There's a chart on the S351 and S390's store page that will show you which option you'll need based on the weight of your sash. 
Comparison of the S351 and S390 balance shoes.
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Emily from SWISCO responded:
August 11, 2021
No problem, Brad! A measurement like that makes me think your shoe was once 1-1/8" deep but wore down from use over the years. It happens quite frequently. In that case, I think you should go with the S390-31. We also suggest weighing your sash to choose the appropriate spring strength option. There's a chart on the S390-31's store page that will show you which option you'll need based on the weight of your sash. If you have any further questions just let us know! |
