Thanks for posting. We judge spiral balance diameter by the outer tube, not the inner spring. The problem it looks like your old spiral balance's outer sheath have worn away, which isn't uncommon with these old plastic versions. Our spiral balances come assembled in a metal tube instead, which is much sturdier.
Since the inner spring looks greater than 3/8" in diameter, I believe you need our Series 600 Spiral Balance, which has a diameter of 5/8"; but if you do have any balance with its outer tube intact, it would be best to measure this to confirm. So long as you measured only the tube up to and not including the colored tip, for the 29" balances you'll need our S600-29 with a blue tip option, and for the 27-1/2" long balances you can round up to use the S600-28, also with a blue tip option. For a new charging tool, see our 75-006.
Excellent. Yes, the Series 600 outer tube actually does tend to measure out as 9/16", but within the trade it is considered 5/8". All orders can be placed via the online store. When you find a part you want, simply click "Add to Cart," and then once you have everything you need, click "Checkout" at the top right hand corner of the screen. Don't forget to set the quantity.
