Block and Tackle Window Balance

Question

I have 3 windows where these appear to be broken and the windows aren't hanging right.  Tip to tip is 27 inches, just the metal is 26inches.  2540 is stamped on it but it appeared there were a number of different series of that size (385, 390, etc.) wasn't sure which ones to order.

Bob · Accepted Answer

Hello there. Based on the end attachments this is most likely either an S378-26, S380-26, or S385-26. The only difference between these channel balances is the shoe depth. See below. Measure your old balance's shoe depth to see what matches best. For a stamp option choose 2530.

Comparison of the S378, S380 and S385 balance shoes.