How to identify an ALUMAX balance?

Hello, thank you for posting,

It appears that the window uses Tilt spiral balances. The window could either use the 5/8" diameter Series 600 or the 3/8" diameter Series 900 spiral balance. You will need to obtain the diameter and length of the metal tube to confirm which series and length is needed. 

Also ask for the colored tip that indicates the strength of the spring. You will need to choose a colored tip option when ordering the item. If the original colored tip does not match up to our options on the product page, you will need to weigh the sash and compare to the strength chart on the page to determine the correct option.

Please let me know if you have any additional questions!