BBs: steel Ø4.5 mm (.177) and airsoft Ø6.0 mm — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/steel-and-airsoft-bbs/  (CC BY 4.0)
Basis: Steel BB .177 calibre (Ø4.5); airsoft 6 mm BB (5.95 ±0.01); drawn as true spheres
Catalog version: 2026-10-20

Sizes: see table below
- A steel BB is Ø4.5 mm (.177 calibre); the file is a Ø4.5 sphere.
- An airsoft BB is nominally Ø6.0 mm, typically 5.95 ±0.01 mm; the file is a Ø6.0 sphere.
- Airsoft BBs are round enough to act as 6 mm balls in a race with a Ø6.0 groove under light load.
- On the can engine I use BBs as low-friction guides for the displacer rod.

ball  dia_mm  note
steel BB  4.5  .177 cal
airsoft BB  6.0  5.95 ±0.01 typical

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Wikipedia: Craft stick — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Craft_stick
- Wikipedia: BB gun — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/BB_gun
- Wikipedia: Table tennis — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Table_tennis
- Long Earth Society: Engine builds (videos and write-ups) — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 2 parts): https://xemstudio.com/files/hardware/steel-and-airsoft-bbs/index.json
API: https://xemstudio.com/api/geometry?object=steel-and-airsoft-bbs