What do I order

Thanks for writing in. This looks like either a S351-28 or S390-28. The only difference between these two balance Series is the 'depth' of the bottom nylon shoe. The Series 351 bottom nylon shoe has a depth of 1", whereas the Series 390 bottom nylon shoe has a depth of 1-1/8". Compare with your old balances and see what you think matches best.

Once you know which balance you'll need, you need to pick a stamp option. I see you have '2730' written in marker on the balance. Is that number stamped elsewhere on the metal channel? If so, choose a stamp option of 2730, for a window sash in the weight range of 13 through 19 lbs. 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.