Cartridge balance question

Thanks for posting. Your balances look like they could be either the S380-28 with a 1" shoe or the S385-28 with a 1-3/32" shoe, which both have a channel length of 28". To determine which series is needed for your window, look over the dimensions from the diagram below to confirm the depth of your bottom shoe. Let me know if it does not match either measurement. 

You'll need to select the 2730 stamp for a window weighing 13 to 19lbs.

Comparison of the S378, S380 and S385 balance shoes.

You're welcome! Please feel free to reach out if you had any other questions.