Window Guide Rail & Spring
Hello! Looks like you need a new channel balance. That's what you're referring to as the "slide rail." We sell a wide variety of balances and so I'm confident that we can sell you what you need, but I will require more information before we go any further.
To start, can you remove an undamaged version of the balance in question and show me additional photos? It's important to show an undamaged version to ensure that no important components are broken off or missing. We specifically need a photo of the top fitting, bottom fitting, stamp, and the metal clip at the end of the cord. I also need you to tell me the length of the metal channel and how many altogether you wanted to buy.
The videos below will offer more insight on how these can be removed and replaced, as well as how to properly identify a match.