I have 3 or 4 windows that need to have their balances replaced. However, I didn't find any markings on them, and they don't seem to be like regular channel balances, as they don't have a metal channel. The balances that I've removed have the top plastic piece that holds them to the frame missing, but you can see how those look like in the installed picture (installed_2). The windows can be tilted out only for cleaning or removal. The windows weigh about 17 pounds. I would like to know if you have any balances that I could order that would be suitable replacements. Thank You.