Window sash balance

Both balances look like either an S380-30 or S385-30 to me. 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. 

In either case, you will need to choose a stamp option. Now, both balances are stamped 29-4. This conforms to our stamp option of 2940, which is for a window sash in the weight range of 23 through 28 lbs. This is heavier than both sash weights you cite. Did you ever trouble closing these windows, or keeping them closed, prior to the balances breaking? If so, they might have been too strongly calibrated for your windows, and you'd be better off with a stamp option of 2930 instead (for a sash that weighs 16 through 23 lbs). If you've never had an issue with the windows closing before though, I'd double-check your sash weights. We always recommend replacing the original stamps unless there was clearly an issue beforehand.