Custom corrugated boxes, specified flute by flute.
Corrugated board — a fluted layer between two liners — is what lets a box survive trucks, conveyors and doorsteps. Choosing the right flute and strength rating is the difference between a box that arrives perfect and one that arrives crushed.
- F, E, B, C and double-wall flutes
- Rated by edge crush test (ECT)
- Printed white or kraft liners
- Flute options
- 5
- ECT range
- 23–82
- or white
- Kraft
- Flute
- E (~1/16 in)
- Liner
- White outside
- Rating
- 32 ECT
- Litho-lam or digital
Flute sizes and what they’re for.
| Flute | Approx. thickness | Flutes per foot | Best for |
|---|---|---|---|
| F-flute | ~1/32 in (0.8 mm) | ~125 | Small premium boxes, cosmetic outers, fine print |
| E-flute | ~1/16 in (1.6 mm) | ~90 | Mailer and subscription boxes, retail-ready packaging |
| B-flute | ~1/8 in (3.2 mm) | ~47 | Heavier mailers, inserts, canned goods |
| C-flute | ~5/32 in (4 mm) | ~39 | General shipping boxes, good stacking strength |
| BC double wall | ~1/4 in (6.4 mm) | — | Heavy, fragile or high-value goods; freight |
Smaller flutes (F, E) give a flatter surface for printing and sharper folds; bigger flutes (B, C) give more cushioning and stacking strength.
Strength: ECT and burst.
Corrugated strength is certified on the box maker’s certificate, using either ECT (edge crush test — stacking strength) or Mullen burst (resistance to rupture). Common single-wall ratings and the maximum weight of box plus contents they’re rated for under the standard carrier classification tables:
| Rating | Max weight (box + contents) |
|---|---|
| 32 ECT single wall | 65 lb |
| 44 ECT single wall | 95 lb |
| 48 ECT double wall | 100 lb |
See shipping boxes for the full table and how to choose.
Corrugated box specifications.
| Flutes | F, E, B, C, EB and BC double wall |
|---|---|
| Liners | Kraft (brown) or white; mottled white; coated white for print |
| Ratings | 23–55 ECT single wall; 42–82 ECT double wall |
| Flexo (1–4 colors), digital full color, litho-laminated full color | |
| Styles | Mailers, shipping boxes, display boxes, inserts and dividers |
| Recycled content | Recycled liners and medium available; corrugated is widely recyclable |
Three ways to print on corrugated.
- Flexographic (flexo): ink printed directly onto the board with flexible plates. Most economical for 1–3 color logos and handling marks on larger runs.
- Digital: full color printed directly onto the board, no plates — ideal for short runs and full-coverage designs.
- Litho-lamination: a sheet is printed offset, then laminated onto the corrugated board. The highest print quality on corrugated — photographs and fine gradients — used for premium mailers and displays.
Choosing white or kraft liners.
Kraft liners are the standard and cost least; they suit natural and industrial looks. White liners give bright, accurate color for full-coverage printing. Mottled white is a lower-cost white with a slightly speckled look. For mailers with printed insides, a white inner liner makes inside print pop.
Frequently asked questions
What is the difference between E-flute and B-flute?
E-flute is about 1/16 inch thick with finer flutes and better print quality; B-flute is about 1/8 inch thick with more cushioning and strength. E-flute suits most mailers; B-flute suits heavier or fragile products.
Is corrugated the same as cardboard?
Corrugated board is a specific kind of “cardboard” with a fluted middle layer. It is much stronger than single-layer paperboard for shipping.
What does ECT mean on a box?
Edge crush test — the force the board edge can withstand per inch before crushing. It predicts stacking strength.
Can corrugated boxes be printed in full color?
Yes, using digital printing or litho-lamination for premium quality, or flexo for simpler graphics.
Are corrugated boxes recyclable?
Yes. Corrugated cardboard is one of the most widely recycled packaging materials in the US.
Choose the right flute the first time.
Send the product weight and how it ships. We’ll specify flute, liner and ECT rating.