Scope: reusable personal drinkware people buy to carry water, hot drinks or food — bottles, insulated tumblers, travel mugs and vacuum food jars. Excludes coolers/lunch boxes, jars/containers, dispensers, wine/bar tools and stovetop kettles (sibling leaves).

Seed: the mechanic-equivalent tell is tapping the base — a dented or seal-failed vacuum bottle gives a dull thud instead of a clear ring, and stops insulating even though it looks fine. A mechanic would also flag the lead-solder pellet under the base cap as a wear/failure point: fine while the cap is sealed, a real exposure risk the moment that seam cracks or is pried — the kind of latent-defect thinking a casual buyer never applies to a water bottle.

Sources:
[wikipedia_vacuum_flask] https://en.wikipedia.org/wiki/Vacuum_flask — mechanism: double-wall vacuum blocks conduction/convection, silvering blocks radiant heat, prevents condensation — fetched excerpt
[wikipedia_stanley_drinkware] https://en.wikipedia.org/wiki/Stanley_(drinkware_company) — lead solder disclosure, rival brands not using lead — fetched excerpt
[cnn_stanley_lead_2024] https://www.cnn.com/2024/01/26/health/stanley-cups-lead-wellness — Stanley/CPSC/EWG quotes, 100 ppm federal lead content ban, 15 ppb EPA water action level — fetched excerpt
[switchbacktravel_best_bottles] https://www.switchbacktravel.com/best-water-bottles — capacities per model, "24 hours" cold retention claim, standard-vs-wide-mouth tradeoff — fetched excerpt
[outdoorgearlab_best_bottle] https://www.outdoorgearlab.com/topics/camping-and-hiking/best-water-bottle — spec table: cap/lid type, mouth diameter, cup-holder-friendly, dishwasher-safe, 18/8 steel, straw material, weight (363g) — fetched excerpt
[nalgene_wide_mouth_spec] https://www.nalgene.com/product/32oz-wide-mouth/ — HDPE material, BPA/BPS-free, leak-proof semi-buttress threads, wide-mouth-for-ice claim, "Fits Filtration Devices" spec row, capacities 12–64oz across line — fetched excerpt
[stanley_quencher_spec] https://www.stanley1913.com/products/quencher-h2-0-flowstate-tumbler-40-oz — capacities 14/16/20/24/30/40 oz — fetched excerpt
[yeti_rambler_spec] https://www.yeti.com/en_US/drinkware/rambler/RAM26OZBOT.html — 20oz tumbler, stainless steel construction — fetched excerpt
[wikipedia_water_bottle] https://en.wikipedia.org/wiki/Water_bottle — LDPE named as the flexible plastic used for collapsible/squeeze bottles — fetched excerpt

Branches:
form_factor → bottle: "slows the rate ... contents remain hotter or cooler" applies the same but bottle-specific facets (mouth_width, carry_feature) matter most — switchbacktravel capacity table per bottle model.
form_factor → tumbler/travel_mug: cup-holder fit and straw/chug lids are the deciding spec — outdoorgearlab "Cup Holder Friendly" column and "Chug lid" tester quote.
form_factor → food_jar: no straw, not used in a cupholder — outdoorgearlab spec table shows these columns blank/NA for jar-style entries.
insulation_type → single_wall: cold/hot retention claims don't apply — switchbacktravel notes retention claims only on insulated models.
insulation_type → vacuum_insulated_double_wall: steel grade and lead-seal disclosure become relevant — wikipedia_stanley_drinkware + cnn_stanley_lead_2024 (lead is specifically in the vacuum-seal solder).

Noise:
- Price / list price column (outdoorgearlab, stanley) — price is never a facet per rule.
- "Overall score" / Editors' Choice ranking (outdoorgearlab) — a rating, not a facet.
- Stainless-steel lifetime warranty policy (stanley_quencher_spec) — brand policy, not a product spec.
- "BPA/BPS-free" as its own facet (nalgene) — folded into material facet; near-universal on modern plastics since the 2012 FDA baby-bottle rule, not a differentiator.
- Color/pattern options (all brand pages) — cosmetic, not expertise.
- Standard-mouth aftermarket filter/accessory compatibility — now covered as its own `filter_compatibility` facet (see Corrections); the earlier excuse that it was unconfirmed is wrong, it's on the Nalgene spec page already cited.

Corrections (2026-10-26):
- weight_g range corrected from invented 90–700g to 176–635g, matching outdoorgearlab's own "Measured Empty Weight" row exactly.
- capacity_oz range max corrected from invented 75oz to 70oz (Platypus Platy 2.0L, switchbacktravel); min 12oz re-confirmed on nalgene's own size nav.
- cup_holder_fit backfill_note: removed the invented "~3 in / 7.5 cm" threshold; no cited source states one.
- insulation_type→single_wall branch: removed steel_grade from makes_irrelevant; a single-wall steel bottle still has a grade, so this is gated out of the insulation split rather than wrongly tied to it.
- Added filter_compatibility facet (boolean), cited to nalgene_wide_mouth_spec ("Fits most filtration units...") and switchbacktravel_best_bottles ("filter compatibility at a good price").
- Added collapsible_soft_sided to form_factor.values and flexible_plastic_or_tpu to material.values, cited to switchbacktravel_best_bottles (Platypus Platy, HydraPak Flux) and new reference wikipedia_water_bottle (LDPE/collapsible bottles); added matching vocabulary entries.
- cold_retention_hours: replaced the degenerate 24–24h range with a "typical" note that it is one repeated marketing figure, not a measured spread; no second, genuinely different figure was found in any cited source.
- Relabeled leak_vs_spill_rating source from researched to derived (it's a deterministic rule over lid_closure_type).
- Corrected exterior_finish backfill_cost from low to medium, matching its own stated photo-inspection fallback.
- Added vocabulary entries for HDPE and Borosilicate glass (material facet values that had none).
- form_factor.definition: added a scope clause distinguishing food_jar (vacuum-insulated thermos-style jar) from the sibling "Containers & Jars" leaf's generic storage jars.
- Rejected nothing from check.md's required-fixes list; all 10 items were actioned as above.