S900 balance with blue tip

I have Alcoa, Vinyl, Single Hung, double pane, windows. 21 years old.

The Spiral Balance is a 3/8" diameter, metal tube, approximately 12 inches long, attached to a metal spring, approximately 18 inches long, with a Blue tip. Total combined length is 30 inches.

The window sash is 31"H x 33"W and weighs 19.5 lbs.

Overall window dimensions are 62"H x 34"W.

The closest Spiral Balance that you offer appears to be the S900-30 which is a solid tube, but it doesn't offer a Blue tip option.

I need your expert recommendation for the proper replacement product.

I have included several photos for your inspection.

Thank you for your assistance,

Thanks Paul,
Should I be able to insert the 5/8

Paul recommended the S600-30 balancer.
Unfortunately the channel that the balancer fits in is only 7/16" wide. So, the S600 will not fit.
I've enclosed a photo.
With the previous information provided, will the S900-30 with a green tip be acceptable?
Also, I've got 6 identical windows that I'm repairing. All with the specifications from above. However, I've already removed several balancers and all the lengths vary from 29-1/2 inches to 30-1/4 inches. Are these variances acceptable to replace with 30 inch balancers?