window balance

hello,

I'm looking to replace several window balances.  the pictures are what i took off of one side of the windows I'm working on.any help with what parts to order would be appreciated.

Thanks,

Todd 

Hello,
I’m looking for help identifying the correct window balance coils for my windows.  There are no stamps.
Attached are photos of the window balance I pulled out from one side of one of my windows.  2 coils.  Silver in color.  Coils are ½” wide.  The window sash is 18 pounds.
Thanks.  
I was thinking I can just buy and replace the coils?  I have the silver coils, ½” wide.  The sash is 18 pounds. 
Would this work for my application?
https://www.swisco.com/silver-medium/pd/Series-175-Coil-Balance/S175-SM
I thought my coils were more like S175-SS and S175-SM.  Can you tell me the difference between the S175 and S190 series?
I went with S175 because there is a short coil and a medium coil, with the medium coil having a longer ‘foot’ to attach above the short coil.
Thanks.