Uncertain on which channel balance

Thanks for posting. This appears to be either a Series 351 or Series 390 Channel Balance. The only difference between these two balance Series is the 'depth' of the bottom nylon shoe, so compare both with your old hardware to see what matches best. To confirm what length you need, measure the metal channel not including the end attachments. Finally, you'll need to select a stamp option. Look for a stamp code on the metal channel. If there is no stamp code, or if you're uncertain, weigh your window sash. You can then match that exact weight with one of the weight ranges listed alongside each stamp option on the product page.

See the video below for removal and replacement of channel balances.