A cardboard tube is a spirally- or convolute-wound paperboard cylinder specified by four independent numbers — inside diameter, wall thickness, length, and end-closure — and the right pick is the one whose combination survives the duty (postal impact, label rewind tension, or display handling) without crushing or ovalising [S2].
Birmingham Mailing Cases (BMC), a family-run UK manufacturer operating since 1923, publishes the working envelope most buyers operate inside: 8–500 mm inside diameter, 1–18 mm wall thickness, 5–8000 mm length, with no minimum order quantity on printed tubes and cores [S2]. That range is the de facto spec map for a 100-year-old product class still built from 100% recycled, FSC-certified paperboard with fully recyclable end caps [S2].
Inside Diameter: The Single Most-Constrained Number
Inside diameter (ID) is governed by what must pass through the tube (a rolled A1 poster, a 76 mm label core mandrel, a 3-inch postal document) or by what must wrap onto it (film, paper, textile, foil stock on a rewinding machine). BMC quotes an ID range of 8 mm up to 500 mm as a standard manufacturing window [S2]. Below 8 mm, wall thickness consumes too high a percentage of the OD and crush resistance collapses; above 500 mm, winding machinery and glue-line pressure become the binding constraints and most buyers are steered toward a custom quote. For postal tubes in the UK, 50–80 mm ID is the workhorse band because it accepts A2 and A1 documents without bending.
Cores for industrial winding — paper, film, foil, textile — typically follow the de facto mandrel standards: 76 mm (3 in) is the most common label and tape core, 152 mm (6 in) is standard for mill-finished paper and film rolls, and 305 mm (12 in) is used for wide-web converting lines. If the ID does not match the unwinder mandrel, the core slips or cracks on the first acceleration ramp, regardless of wall thickness.
Wall Thickness and Crush Resistance: 1–18 mm Working Window
Wall thickness on BMC's standard envelope runs 1 mm to 18 mm [S2], and the right pick is set by the stacking, drop, and crush loads the tube must survive. Thin-wall tubes (1–2 mm) are suitable for light-duty postal shipping where the contents are flexible documents; mid-wall tubes (3–6 mm) cover most retail poster mailers; heavy-wall tubes (8–18 mm) are specified for concrete-form tubes, carpet cores, and industrial winding cores where radial crush is the failure mode.
Thicker wall does not automatically mean stronger — the strength gain is dominated by spiral-wound ply count and adhesive bond, and a 6 mm wall of high-density kraft outperforms a 10 mm wall of low-density recycled board on the same drop test. For postal tubes, a 2–3 mm wall on a 50–80 mm ID tube routinely passes a 1 m drop onto concrete with a rolled A2 document inside; for a concrete-form application the wall jumps to 6–10 mm and the ID opens to 200–300 mm.
Length: From 5 mm Plug to 8000 mm Concrete-Form Tube
BMC's published length range is 5 mm to 8000 mm [S2]. The 5 mm end of the range is essentially a cardboard plug or spacer, not a shipping tube; the 8000 mm end is the concrete-form / piling-tube territory where the cylinder is used as a sonotube and cut to length on site. Postal tubes typically sit in the 300–1000 mm band; industrial cores for converting lines run 1000–3000 mm; concrete-form and piling tubes run 3000–8000 mm.
Length interacts with diameter through the slenderness ratio (L/ID): above roughly 100:1, even a thick-walled tube will ovalise under its own weight during handling. A 1000 mm postal tube with a 76 mm ID sits at about 13:1 and handles cleanly; an 8000 mm concrete-form tube at 300 mm ID sits at 27:1 and needs cradle support on every lift.
End Caps and Closures: Plastic Plug, Metal Plug, Shrink Band, or None
End-closure choice is the most often missed selection criterion, and it dominates the cost-per-unit as much as the tube body itself. The four working options, ranked roughly by cost and tamper-resistance, are: (1) no cap, (2) plastic end plug (most common on retail postal tubes), (3) metal end plug with crimp (used on heavy-duty document tubes and some industrial cores), and (4) heat-shrink plastic band (used on concrete-form and large-diameter industrial tubes). BMC now offers eco-friendly cardboard end plugs as a recyclable alternative to plastic plugs [S2].
For a postal tube that ships a single rolled document, a plastic plug is the default and the cost adder is roughly 10–20% of the bare tube. For a label or tape core that mounts on a sprung mandrel, the end must be a clean, square cut with no plug, or the mandrel will not seat. For a concrete-form tube, the end is usually left open and squared because the cap is cast into the concrete.
Material and Print: 100% Recycled, FSC-Certified, MOQ-Free
BMC states that all tubes are made from 100% recycled material and sourced from FSC-certified paper mills, and that tubes (including end caps) are 100% recyclable [S2]. The same manufacturer offers bespoke print on the outside or inside of the tube with no minimum order quantity [S2], which removes the usual barrier that small buyers face when trying to put a brand on a custom postal tube. This combination — recycled stock, FSC chain-of-custody, MOQ-free print — is the closest thing to an industry baseline for European-manufactured tubes in 2025–2026.
Buyer tip: ask the manufacturer for the FSC certificate number, the recycled-content percentage verified by the paper mill (not just the converter), and confirmation that the adhesive is water-based and repulpable. Adhesive choice is invisible until the tube hits a paper-recycling pulper, and solvent-based glues will contaminate the batch.
Selection Logic: Postal, Core, or Display Duty
Three decision trees cover the practical majority of industrial and commercial buyers. (1) Postal / document shipping: pick ID to match the rolled document plus 5–10 mm clearance, 2–3 mm wall, plastic or eco-cardboard plug, length set by document plus 30–50 mm headroom; (2) Industrial winding core: ID must match the unwinder mandrel exactly (76, 152, or 305 mm), wall 6–12 mm to survive rewind tension, no end plug, length set by web width; (3) Display / presentation / concrete form: ID set by the object being held, wall 4–10 mm, length cut to order, end-closure optional. Buyers who skip the ID-to-mandrel check on cores, or who specify a wall under 2 mm on a postal tube heavier than 400 mm long, are the ones who see crushed goods on arrival [S2].
Trackable signals for the next 6–12 months: any revision to FSC chain-of-custody rules affecting recycled-content claims, and any move by major UK or EU retailers to mandate cardboard end plugs over plastic on retail-pack postal tubes — both would shift the spec map materially. For related industrial spec work, see manganese ore sourcing and gear motor selection.
Spec-level background on the components involved: pressure transmitter, flow meter, and industrial valve.