properties /measurement

THE INSIDE (SEALING) DIAMETER OF THE FILLER NECK THE CAP SEALS AGAINST, as a numeral with a length unit - the dimension that decides whether a cap fits at all. Motorad's field is `Filler Neck Inside Diameter` and it prints 1.53 in / 38.86 mm for the T16 and 1.54 in / 39.12 mm for the ST16, with `Valve Outside Diameter` repeating the same figure. IT IS NOT THE NECK'S OUTSIDE DIAMETER [A-6], which the same house publishes on the same page as a DIFFERENT number - `Filler Neck Outside Diameter` 1.97 in / 50.04 mm on the T16 and 1.99 in / 50.55 mm on the ST16 - and which this slot does not hold; one witness only, so it is recorded as an obligation rather than minted, on b156's Attachment-Type standard. THIS IS THE BEARING'S TWO-CONCENTRIC-CIRCLES PROBLEM IN THIS BATCH'S OWN WORDS, left undone one class away until the adversary found it: a slot that could not say which circle it held would make 38.86 and 50.04 the same statement. IT IS NOT A FITMENT [REFINE-LOG 2026-08-25] and the test is the one `thread_size` already passes: a neck diameter names a dimension of the part in the hand, no vehicle, no model and no maker, and nothing about the cap changes when a model is discontinued - where `Braking system: Sumitomo` on a brake pad names the caliper's MAKER and is therefore a cross-reference [H4-f9]. The trade's `A size` and `B size` neck designations are this number under a letter, and the letter is not minted as a token because no maker read at the mint publishes the series as a field - Stant states `3/4 inch deep A size filler neck` only in free prose. Concern measurement.