Carbon fibre square tube (box section) sizes, 4 to 20 mm — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/carbon-fibre-square-tube-sizes/  (sheet CC BY 4.0)
Basis: Maker's product listings (Easy Composites box section)
Catalog version: 2026-10-20

Sizes: see table below
- Square carbon tube (box section) as listed: outer size, inner size and wall in mm. Lengths 1000 mm (4 and 6 mm) or 1000 / 2000 mm.
- Tolerance stated for the 6 × 4 section: ±0.25 mm on outer and inner size.
- No file: the corner radii are not published, and a square section drawn with invented corners would not be the real fit.

outer mm  inner mm  wall mm
4  2.5  0.75
6  4  1
8  7  0.5
10  8  1
20  17  1.5

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Easy Composites: Carbon fibre box section (category: outer and inner size in each title) — web — Publisher's page; dimensions are facts — https://www.easycomposites.co.uk/carbon-fibre-box-section
- Easy Composites: 6mm (4mm) carbon fibre box section (OD / ID tolerance 0.25 mm) — web — Publisher's page; dimensions are facts — https://www.easycomposites.co.uk/6mm-4mm-carbon-fibre-box-section
- Easy Composites: Technical datasheet: carbon fibre pultrusions (tube, rod, strip, box section sizes) — web — Publisher's page; dimensions are facts — https://media.easycomposites.eu/datasheets/EC-TDS-Carbon-Fibre-Pultrusions.pdf

No true-size file yet: the published figures do not fix the whole shape; a measured scan is planned.
API: https://xemstudio.com/api/geometry?object=carbon-fibre-square-tube-sizes