Sizing my spiral balances

I watched your video on sizing spiral balances, but I have a question. My existing balances have a vinyl cover over a tube of sorts (when I cut back the vinyl I see what appears to be a coiled metal tube that the spring is in. The issues comes when I measure. If I measure from the top of the tube down to the bottom of the tube (not including the balance tip), it is 28-1/2". If I measure to the bottom of where the vinyl ends, it is 29". Also, the diameter of this "tube" looks about 7/16". Photo attached.

Based on my interpretation, I should order a 3/8" x 29" with a red tip.

Does this sound correct?

After doing more research and re-measuring, I understand that with the plastic tubes, I need to measure the plastic tube length and not the internal metal tube.

Based on that, the length is 29" and the diameter is 9/16" which indicates I need the S600 x 29 (red).

Let me know if you concur. Thanks!