Balance for single hung window

Hey there!

It appears you want either the Series 380 or Series 385 based on what I see in your photos. You'll have to measure as shown below to determine the best match. There should also be a stamp on the metal channel that will tell you what option you'll need to select for your replacements.

Comparison of the S380 and S385 balance shoes.

No the "hemmed" portion and the bumps you're referring to won't affect function. The number stamped on your balance represents the spring strength it's calibrated to support. Your 21 9 stamp is from an older rating system that we don't use so you'll need to weigh the window sash on a scale to determine the proper stamp. There's a chart under the product description on the S385-22 store page that will show which one is best for your replacements depending on the sash weight. 

I hope this is helpful! Let me know if you have any other questions.