window balance spring replacement 31 inches block and tackle stamp 3040 5/8 channel

Question

Hello - I'm trying to identify the correct replacement part. My subject line above has the details. Also, the stamp on the back of the part reads: 30 4 FT CMC 2. This part clearly broke in one of my windows; however, I have many windows that are difficult to open so I may need more than just his one.

Jasmine · Accepted Answer

Hey there,

Your window balance is likely to be match for either the S380-31 or the S385-31. To determine which of these is the series you have, you'll need to measure the depth of the bottom shoe.

Our 3040 stamp should work for you window. A pair of these will support a sash weighing 23 to 28lbs.

Comparison of the S378, S380 and S385 balance shoes.