No markings on spiral balance

Hello,

Your photos resemble the (3/8") S900 or (5/8") S600 spiral balances, depending on the diameter of the plastic housing tube. Make sure to confirm the spiral end matches yours since it's a bit tough to make out in your photo.

How to measure the tube length of the S600 spiral balance.

You'll also need to weigh your sash to determine which color option you'll need. There is a chart on the product page that explains how to choose your option based on the sash weight. Thanks for posting!