When you order custom boxes, sooner or later the question of the flute comes up: E, B, C, or maybe double-wall. Knowing the types of corrugated cardboard is not insider knowledge — it is a practical decision that affects the stiffness of the packaging, the print quality, the weight of the parcel and the price per unit. Below we lay out the types of corrugated cardboard — the individual flutes — side by side, so that after reading you will know not “which one is best” (because that is the wrong question), but which one suits your product and shipping method.
What corrugated cardboard is and what it is made of
Corrugated cardboard is a layered material: flat sheets of paper (called liners, i.e. the facings) and a wavy layer of paper in the middle — that is precisely the “flute”. This simple arrangement delivers a surprising amount: the flute acts like a series of arches that stiffen the flat surface and cushion impacts, while weighing very little, because inside there is mostly air. The taller and more widely spaced the flute, the more cushioning and bending stiffness; the lower and denser it is, the smoother the surface and the better the print.
In practice you will come across two main construction variants. Three-layer cardboard (single-wall) is two liners and one flute between them — light, versatile, the most common in packaging. Five-layer cardboard (double-wall) is three liners and two flutes — thicker, heavier and considerably stronger, for special tasks. The flute itself differs above all in height, and almost everything else depends on that.
Types of corrugated cardboard — E, B, C flutes and double-wall BC
Flutes are designated with letters that indicate the height of the profile. The thicknesses below are given approximately — these are general industry, ballpark values, not rigid parameters; we always select the actual specification for the specific project.
- E flute (microflute) ≈ 1–1.5 mm — low and dense, giving a smooth surface and the best print among the flutes. It is the first choice for light retail and e-commerce packaging where appearance matters.
- B flute ≈ 2.5–3 mm — good surface stiffness and resistance to crushing. It works well in shaped boxes and everywhere the wall needs to “hold its form”.
- C flute ≈ 3.5–4 mm — versatile, with good cushioning. A classic for shipping cartons and slotted boxes.
- Double-wall cardboard (e.g. BC) ≈ 6–7 mm — five-layer, the strongest. For heavy, large products and for shipping that has to survive many transfers.
It is also worth mentioning F microflute (below 1 mm) — the lowest profile, used in thin, “paper-like” retail packaging where minimal thickness and aesthetics are the point. It is a niche, but it can be helpful for very light products.
Types of corrugated cardboard — a table comparison
The differences show up fastest when set out point by point:
| Flute | Approximate thickness | Features | Typical application |
|---|---|---|---|
| E (microflute) | ≈ 1–1.5 mm | Smooth surface, best print, light | Retail packaging, light e-commerce boxes |
| B | ≈ 2.5–3 mm | Good wall stiffness, resistance to crushing | Shaped boxes, packaging that holds its form |
| C | ≈ 3.5–4 mm | Versatile, good cushioning | Shipping cartons, slotted boxes |
| Double-wall (BC) | ≈ 6–7 mm | Five-layer, greatest strength, heavier | Heavy and large shipments, products requiring protection |
| F (microflute) | < 1 mm | Very thin, smooth, aesthetic | Thin retail packaging, very light products |
Thickness, stiffness and weight — how the flute affects protection
This is the most important practical point. A taller flute means more material in the vertical, i.e. more cushioning and bending stiffness — but also more thickness and greater parcel weight. C flute and double-wall BC “work” under downward pressure and impacts, which is why they go into shipping and heavier contents. The low E flute, on the other hand, is compact and flat: it protects worse under heavy loads, but it keeps a slim, elegant wall for a light product.
Protection is always a compromise between strength and weight and volume. The harder the parcel’s journey — more transfers, stacking on a pallet, pressure from other shipments — the more this shifts toward C flute or double-wall. For light products sold mainly in-store, this topic recedes into the background and appearance decides. We always set the choice of flute and grammage to the weight and shipping method of the specific product — it is part of the design, not guesswork.
Flute vs print quality — why E wins
Here the difference is clear. The lower and denser the flute, the smoother the surface — and a smooth surface means better, sharper print. That is why E flute is the first choice when the packaging is meant to make an impression: full colour coverage, fine details and the logo come out cleanest on it. On taller flutes (B, and especially C), full coverage can produce a “washboard” effect — a subtle rippling visible on the printed surface, because the flute “shows through” the thin liner.
This is not a flaw but a division of roles: E for presentation and print, C and double-wall for transport and protection. Full, photographic printing is rarely done on shipping cartons — a logo or a simple single-colour print is usually enough there. If you care about both appearance and protection of a heavier product, a good arrangement is often a shaped box of E or B flute inside and a strong slotted box of C flute outside. We write more about printing itself in printed packaging.
Which flute to choose for which application
If you are not sure, go through the questions:
- Light retail packaging or a light e-commerce parcel that has to look good? → E flute (possibly F for very thin ones).
- A shaped box that has to hold its form and take a nice print? → E or B flute.
- A shipping carton or a slotted shipping box? → C flute.
- A heavy, large product or a long journey through couriers and transfers? → double-wall BC cardboard.
- Premium for courier shipping? → often two layers: a shaped box of E/B inside, a slotted box of C or BC outside.
In practice many brands combine flutes in a single project — a slim, well-printed shaped box for the product and a strong shipping carton around it. If you are only just sorting out packaging types, start with the guide to types of cardboard packaging, and for details look at the offer of cardboard boxes.
Flute vs cost — what to actually look at
Do not look at the price per unit through the lens of “which flute is cheapest”, but rather how much material a given construction consumes. A taller and thicker flute means more paper and greater weight, which raises both the material cost and the shipping cost. Double-wall BC will be more expensive than a single E flute at the same dimensions — but it provides protection that E simply cannot deliver for a heavy product. Overpaying for flute “just in case” is a cost with no return; underestimating ends in crushing during transport.
Regardless of the flute, the same run mechanics apply: the larger the quantity, the lower the price per unit, because the fixed preparation costs (design, cutting die, machine setup) are spread over more units. We start from 500 units, and the construction and print design as well as the visualisation for approval are done at no extra charge. What exactly influences the final amount, we break down in the guide how much packaging with a logo costs.
Frequently asked questions
How many layers does corrugated cardboard have?
Most often three (two liners and one flute) — that is three-layer, single-wall cardboard. Thicker five-layer cardboard has three liners and two flutes (e.g. double-wall BC) and is considerably stronger.
Which flute is best for printing?
E flute, i.e. the microflute. It is low and dense, so it gives the smoothest surface and the sharpest print — which is why it goes into retail packaging and light e-commerce. On taller flutes, subtle rippling may be visible under full coverage.
Which flute for shipping heavier products?
C flute for standard shipping cartons, and for heavy, large products or a long journey — double-wall BC cardboard. These give the greatest stiffness and cushioning.
How does flute differ from grammage?
The flute is the profile (height) of the corrugated layer and determines thickness and stiffness. Grammage is the weight of the liner and flute paper. Strength depends on both — which is why we select them together for the specific product.
Are the thicknesses given here Sabona’s parameters?
No — these are approximate, general industry values that help you get oriented. We select the actual flute, grammage and construction individually for the product’s weight and shipping method.
Choose the flute for your product
The best test is the specifics: give us the product, dimensions and shipping method, and we will suggest the flute and construction and prepare a preliminary quote.
→ Choose the flute and calculate the cost
See also
Choosing material and construction? Start with the guide to types of cardboard packaging, check the offer of cardboard boxes and the comparison of shaped boxes vs slotted boxes. Shipping in parcels? See e-commerce shipping boxes, and how much it costs — we break it down in the text how much packaging with a logo costs. We are a packaging manufacturer from Warsaw — we do the design and visualisation at no extra charge, we produce from 500 units and ship across all of Poland.