I came across your website via someone else who had a video on window repairs. I am looking to repair/replace my non-tilt window balance springs on four windows. They are all the same size and I have removed the balance springs and they all match. The spinrgs go in an half inch (1/2") channel and are 34 inches long. The number stamped on the side is "3390 35". Looking at your products my guess is the series 390 but I am uncertain. Hope this helps! Any question, please let me know. Thanks!!
Dane
