Corrugated board is a sandwich: a wavy fluted sheet glued between two flat liners. The size of the wave, called the flute profile, determines the board's thickness, strength, cushioning and print quality. Choosing the right one saves money and prevents damage.
Flute profiles at a glance
| Flute | Thickness | Flutes per foot | Strengths | Typical use |
|---|---|---|---|---|
| F (micro) | 0.8 mm | ~125 | Finest print surface, very thin | Small retail boxes, cosmetics |
| E | 1.5 mm | ~90 | Excellent print, light protection | Mailer boxes, retail-ready packaging |
| B | 3 mm | ~47 | Good crush resistance, decent print | Shipping boxes, die-cut mailers |
| C | 4 mm | ~39 | Best cushioning per cost | Standard RSC shipping boxes |
| BC (double wall) | 7 mm | B + C | Very high stacking strength | Heavy, fragile, export |
| EB (double wall) | 4.5 mm | E + B | Strong and still printable | Premium shippers |
ECT vs burst test
Corrugated is graded two ways. ECT (Edge Crush Test) measures stacking strength, the force needed to crush the board on its edge. Burst (Mullen) test measures puncture resistance. Modern shipping is mostly about stacking, so ECT is the more useful number.
- 32 ECT: the standard single-wall grade for boxes up to about 30 lb.
- 44 ECT: heavier single wall, up to about 65 lb.
- 48 ECT double wall: up to 80 lb and beyond, with far better resistance to crushing on pallets.
Which flute for which box
Mailer boxes: E-flute is the default. It prints almost as well as paperboard, folds crisply and protects apparel, cosmetics and books. Use B-flute for products above 5 lb or with hard edges.
Shipping boxes: B or C flute at 32 ECT for most goods. C-flute cushions better; B-flute prints better and takes up less warehouse space.
Heavy or fragile: BC double wall at 48 ECT. Glassware, ceramics, machinery parts and anything exported by sea.
Retail-ready cases: E or EB, because the outside is printed and will be seen on shelf.
Liner colour and print
The outer liner can be kraft (brown), white top (bleached outer liner), or mottled white. White liners cost slightly more and make colour printing accurate. Kraft with one or two ink colours is the most economical branded look and is fully recyclable.
Full-colour printing on corrugated is done either direct (flexo, for simple graphics) or litho-laminated, where a printed paperboard sheet is laminated to the corrugated. Litho-lam gives photo-quality results on mailers and retail-ready cases.
Sustainability
Corrugated is the most recycled packaging material in the world. Our boards contain recycled fibre, are FSC-certified on request and are curbside recyclable. Avoid film lamination if recyclability matters; use aqueous coating instead.
Get a recommendation
Tell us the product weight, dimensions and how it ships. Our engineers pick the flute and ECT grade, and you can price it instantly before requesting a formal quote.