Which is the Right Channel Balance

Can you give me clearer photos of the nylon fittings at both ends? Can you also confirm the exact metal channel length? Finally, is there any stamp code on the metal channel? We'll do our best to narrow this down from there. Thanks. 

Thanks for this. If the metal channel, not including the fittings, is 27" long, then you need either an S351-27 or S390-27. The only difference between these two balances is the bottom nylon shoe depth, so compare both with your old hardware to see what matches best. You'll then need to choose a stamp option. Look for a stamp code on the metal channel. If there is none or you are uncertain, obtain the exact weight of your window sash. You can then match that exact weight with one of the weight ranges listed alongside each stamp option on every balance's shop page.