channel balance for double hung non-tilt window

Hi there, thanks for posting. The Series 351 and Series 390 are almost identical besides for their bottom shoe attachments. The Series 351 uses the 15-002 that has a depth of 1" while the Series 390 uses the 15-001 with a depth of 1-1/8". You'll need to measure to determine which one will work for you. Hope this helps!