Spiral Balance

My windows are from 1966 Sashes move in a plastic track with plastic tubes (all plastic brittle and cracking), metal springs and plastic treaded spiral balancers.
Most springs have detached from their sashes so windows require propping.
I want to replace with modern spiral balance.

The window frames and sashes are wood.

Sashes are 8.15 pounds each and measure 36 inches wide and either 18 inches high (lower) or 17 inches high (upper)

My windows are double hung, NON tilt.

Current spiral balances have a 3/8 inch track.
Springs are 11.5 inch inside a 16.5 inch plastic tube that is 3/8 inch wide.

The old spirals have no color code.

Existing framing is smooth wood so all hardware for mounting will be required.

Can you help me identify appropriate spiral balances? Thank you.

I have separated the balance unit in photo to show spring that engages plastic spiral rod. When assembled spring coil at one end clips to top end of plastic tube. Spring is inserted into white plastic tube. Flat end of plastic spiral rod protrudes from other end of tube

Since first email I found local vendor and successfully installed on one window. I still wish to purchase from Swisscom.

I think I need blanches that are for non tilt window, five eighths with 15 inch and 17 inch tube lengths for upper sash and lower sash respectively. I used local tubes of 16 and 17 with white collar but from your website I think red collar is correct. Check original email for measures and let me know if you agree with this choice. To summarize double hung, non tilt, 15 inch tubes on upper sash, 17 inch tube on lower sash, red collar to match window weight, series 500 t bar model, crows foot catch.

When we agree I will proceed to order.