Tools
Nothing here works yet, and that is deliberate.
A sizing calculator that guesses is worse than no calculator at all, so this section stays empty until there is enough measured device data behind it to make one honest. In the meantime the sizing guide carries a printable measurement worksheet and static conversion tables, which is what an accurate answer looks like today.
When tools do land here they will be built on the measured specifications the review programme is set up to collect — internal diameter, tube length, gap, ring inner diameter and weight, taken by hand with callipers rather than copied from a listing. The first devices have not been measured yet.
What is planned
Sizing calculator
In development — not startedTurns three measurements into a base-ring diameter and a cage length range, with the reasoning shown rather than hidden. It is waiting on enough measured devices to be right more often than a printed worksheet, which is a higher bar than most calculators in this niche clear.
Ring-size lookup
In development — not startedCross-references what a manufacturer prints on a ring against what the ring actually measures, so a "45 mm" from one brand can be compared with a "45 mm" from another. It needs the calliper database behind it before it means anything.