properties /identity

WHAT SHAPE OF FRICTION PART THIS IS, and it is the single most important op in this batch because it is what a class was NOT minted for. A disc brake pad, a drum brake shoe and a loose drum brake lining are three forms of one thing — a friction body pressed against a moving surface to turn motion into heat — and the trade sells them as three goods. UNSPSC agrees with the trade and files pads at 25171713 and shoes at 25171712. THE POOL FILES THEM AS ONE KIND ANSWERING THIS PROPERTY THREE WAYS, on the 2026-08-25 amendment and on the settled campaign precedent: b153 folded air, cabin-air and fuel filters into `filtration_duty` values and b154 folded five named fluid trades into `fluid_duty` values, and the test both times was whether the sub-kind published a fact its siblings could not. A shoe publishes exactly one such fact, its drum diameter, and one exclusive slot is the very thing H1-f6 put `OilFilter` on permanent notice for; a pad publishes none at all, since a shoe can carry a wear sensor too (heavy commercial drum brakes are sold with them). So no child is minted and the form is a value. Required, because it is the fact that tells the two apart and nothing else in the grammar does. NOT a fitment [REFINE-LOG 2026-08-25]: naming a part's own shape names no vehicle, and which brake it suits — disc for a pad, drum for a shoe — is READ off this value and must never be stored a second time [A17]. Filed under identity, so not axis-eligible: a pad and a shoe are two listings, never two cells of one buy box — the filing `filter_form`, `filtration_duty` and `drinkware_type` already carry.