Scope: "Bats" = swung bats for bat-and-ball sports — baseball, fastpitch softball, slowpitch softball, and cricket. Excludes table-tennis/racquet bats (Racquets & Paddles leaf), balls (Balls leaf), batting gloves/pads/helmets (Protective Sports Gear leaf), and canoe/kayak paddles (Paddles & Oars leaf).

Seed: Equivalent of steel_hardness is drop_weight (weight_oz − length_in): the single number that trades swing speed against power, and most beginners shop by length or looks instead. A bat fitter's first move, before material or price, is checking the certification stamp (USA Bat/BBCOR/USSSA) or willow grade/MCC Law 5 compliance — a great bat that's not legal for the buyer's league is useless regardless of spec.

Sources:
[wikipedia_baseball_bat] https://en.wikipedia.org/wiki/Baseball_bat — drop formula, MLB max diameter/length, one-piece wood rule, HS drop/diameter caps — fetched excerpt
[wikipedia_composite_bat] https://en.wikipedia.org/wiki/Composite_baseball_bat — BBCOR -3 drop + 2-5/8in rule, USA Bat vs USSSA 1.15 BPF, break-in/cold-crack — fetched excerpt
[wikipedia_cricket_bat] https://en.wikipedia.org/wiki/Cricket_bat — Law 5 dimensions, willow types, grain count 8-12 ideal, handle material cap, sizes 0-6/Harrow/SH/LH — fetched excerpt
[wikipedia_softball] https://en.wikipedia.org/wiki/Softball — softball bat max 34in/2.25in/38oz, 2-1/4in standard diameter — fetched excerpt
[usabat_official] https://www.usabat.com — USA Bat standard framing, approved-list lengths 27in+ and 2-5/8in max diameter — fetched excerpt
[lords_mcc_law5] https://www.lords.org/mcc/the-laws-of-cricket/the-bat (via web.archive.org snapshot, live site 404'd) — Law 5.7 length/width/depth/edge/handle numbers verbatim — fetched excerpt
[cricketstoreonline_buying_guide] https://cricketstoreonline.com/pages/the-cricket-equipment-buying-guide-gift — willow type/grade framing, junior sizing, adult weight 2lb7oz-3lb, sweet spot — fetched excerpt
[cricketstoreonline_bat_guide_2026] https://cricketstoreonline.com/blogs/guides/cricket-bat-guide-2026-how-to-choose-prepare-master-your-bat — pro weight examples, grade price tiers, grain count 6-9 ideal — fetched excerpt
[graynicolls_size_guide] https://www.gray-nicolls.co.uk/pages/size-guides — bat size 0-6/GEM/Harrow/SH/LH table by height/age — fetched excerpt
[graynicolls_willow_story] https://www.gray-nicolls.co.uk/blogs/the-game/the-willow-story-from-source-to-century — master grading by hand, pick-up/weight/balance framing — fetched excerpt

Branches:
sport=cricket makes certification_stamp/barrel_diameter/drop_weight/barrel_wall/swing_balance/construction/handle_shape/material irrelevant — cricket has no drop-weight concept and is wood-only by law (wikipedia_cricket_bat).
sport=baseball/softball makes willow_type/willow_grade/bat_size_cricket/bat_weight_cricket/sweet_spot_position/edge_thickness_mm/handle_material irrelevant — those are cricket-specific willow-blade specs (wikipedia_cricket_bat, cricketstoreonline_buying_guide).
player_level=professional_or_elite_amateur makes certification_stamp irrelevant — pro/elite play requires solid wood or top willow grade, not a youth/amateur performance stamp (wikipedia_composite_bat: "MLB or affiliates ... does not allow composite" outside approved exceptions; usabat_official covers amateur/youth only).

Noise (spec-sheet rows seen but not made facets):
- Grip type, toe guard, anti-scuff sheet (cricketstoreonline_buying_guide) — cosmetic/accessory finishing touches, not a buying-decision spec.
- Knocking-in requirement, linseed oil maintenance (wikipedia_cricket_bat) — a care process after purchase, not a spec; kept as vocabulary instead.
- Fungo bat (wikipedia_baseball_bat) — a separate coach's-practice-tool subtype, out of scope for a buyer choosing a playing bat.
- Pine tar placement rule, corking/altering bats (wikipedia_baseball_bat) — in-game conduct rules, not product specs.
- Bat color/stain, player endorsement signature (wikipedia_baseball_bat) — cosmetic only.
- Torpedo bat shape (wikipedia_baseball_bat) — a 2025 MLB barrel-profile variant within standard legal dimensions; noted in vocabulary, not a separate facet since it doesn't change any certified spec.

Corrections (2026-10-26):
- Removed uncited `asa_isa_1_20_bpf` from `certification_stamp`; research showed ASA/USA Softball is actually an exit-velocity standard (98/100 mph), not a BPF number, so it couldn't be re-added as-is.
- Split softball's certification stamps into a new facet `softball_certification_stamp` (USA Softball/ASA exit-velocity, NSA/ISA/USSSA 1.20 BPF, unregulated), sourced to axebat_bat_certification_guide and baseballmonkey_bat_certifications, so fastpitch/slowpitch branches no longer offer or backfill baseball-only `certification_stamp` values.
- Added `spine_height_mm` facet for cricket (55-70mm typical, up to 75mm high-spine), sourced to cricketstoreonline_bat_guide_2026 and the new topcricketstore_spine_height_guide.
- Reworded `player_level`'s split question and cold_start_question to list a fourth option ("pro/elite") so the professional_or_elite_amateur branch is reachable from the question text.
- Added vocabulary entries for Cleft, BPF, and Harrow.
- Reworded `barrel_diameter`'s why_experts_care: the 2-3/4in cap is PONY League/Cal Ripken League (youth travel-ball), not "adult rec leagues" — per wikipedia_baseball_bat.