Identify Window Balancer Please

Thanks for writing in. It looks like you have either the Series 380 with a 1" shoe or the Series S385 with a 1-3/32" shoe. 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. 

Comparison of the S380 and S385 balance shoes.

For the 19" balance you'll need to select the 1840 stamp, for a 14 to 17lb  and for the 28" balance, you'll need to select the 2740 stamp, for a 19 to 26lb window.