need help on wich one to order

Thanks for reaching out to us! Our Series 500 comes to mind but the outer tube diameter is 9/16" (considered 5/8" in the trade). Can you double-check that measurement for us? 

The old white tip is part of an outdated system so you'll need to weigh the window sash on a scale and refer to the chart under the product description on the S500-17 store page to determine the proper option for your replacement balances. 

The Series 500 is compatible with many brackets and shoes but the best match will ultimately rely on the original. Do you have an identical window in the house? If so, we recommend checking that window for an intact shoe or bracket. Seeing a photo of that will help us narrow down some options.