block and tackle window parts

Hello,

With this combination of attachments, you could have either the S380-29 or S385-29 channel balance. You’ll need to measure as shown below. The Series 380 has a 1" bottom attachment, and the Series 385 has a 1-3/32" attachment. 

Your 28F stamp would generally correspond to our 2860 spring strength options for these replacement balances. With that being said, it would be a good idea to confirm that your sash falls within the  32 to 35 lbs weight range that this strength code would support. Thank you and let us know if you have any other questions or concerns.

Comparison of the S380 and S385 balance shoes.