Not Sure What Size Weatherstripping I Need

I'm afraid I can't tell what size you need, either. You will need to remove a sample of the wool pile in order to get the most accurate measurement. Keep in mind your sash might be screwed together at the corners. If it is, remove the screws and slightly pull the frame from the glass so you can slide the wool pile from the sash frame. Just be careful as you don't want the frame to come apart. Once it's out, you can compare your dimensions to those on our site here.

Perfect, thanks! I believe you can use our 58-022 white wool pile weather stripping for your window sash. I would just give our dimensions a look to be sure.