Balance Question

Question

What is the difference between 407 Series 170 and 407 Series 171? How can I tell which one I have? I only see "407" stamped on the spring. Thank you.

Paul · Accepted Answer

The S170-407 is meant to replace balance systems that use only one coil spring on each side of the sash. The S171-407, on the other hand, has an extended "tongue" so you can piggy back the spring on top the S170-407 in the cases where there are two springs on each side of the sash.