identify spiral balance

Hello there. I'm confident we can help, but we'll need more information. Is this for a tilt or non-tilt window? If it's a non-tilt window, I will need to see a picture of the tip. Is the spiral balance's outer tube 3/8" in diameter, or 5/8"? With that information, we should be able to narrow this down. 

Perfect, thank you. In that case, go with the S600-33, with a black tip. Let us know if you have further questions!