Window channel help

Thanks for reaching out. Based on your photos it appears you have either the S351-21 or the S390-21 with a 2040 stamp. To confirm the series need for your window, you'll need to confirm the measurement for the depth of your bottom shoe. I would also be sure to confirm that the length of your metal channel is 21" (not including the plastic attachments), given you have the 2040 stamp.

Comparison of the S351 and S390 balance shoes.