Channel Balance
Hello, thank you for posting,
It appears you have either our Series 351, with a 15-002 bottom attachment, or Series 390, with a 15-001 bottom attachment. Take a look at the image below to determine which balance you'll need.
When determining the length, only measure the metal channel excluding the nylon attachments. Once you have the length, you will need to weigh the window sash on a scale. From there compare to the strength chart on the product page to confirm the correct stamp option to support the sash.
The caps being referred to are called top sash guides. For the top sash guide, we will need to see it removed from the window where we can see a front and side view. Thank you!