Need replacement spiral balance rod

Hi,

We have these two double sash wooden windows as seen in the first photo. The two lower sashes (the only ones we're concerned with) each use 2 spiral balance rods, which have become defective. We'd like to replace them but need to get new spiral balance rods.

The lower sashes are 32"W x 27 3/4"H. and the full height of the window is 54".

The remaining photos show 1) a removed spiral balance rod, 2) a close-up of the top of the rod, 3) a close-up of the bottom of the rod and bracket, and 4) a view of a rod properly attached at the top.

The tube is 27" long and 9/16" in diameter. I don't see any colored tip. The bracket is 2 1/2" long and 3/8" wide.

What do you recommend as a replacement spiral balance rod and related hardware for these windows?

Thanks very much.
Dennis

Thanks Paul. I had a feeling you would recommend the Series 500, but wanted to wait until you replied before ordering.

BTW, I ordered the red tip because I was not sure of the sash weight and assumed that a 32" x 27 3/4" sash should weigh between 7 and 29 lbs.

Does that seem like a reasonable assumption?

Thanks,
Dennis