Corrugated flute types A, B, E & AB explained
The flute is the wavy heart of every corrugated box. Its profile decides how thick, cushioned, strong and printable your carton is. This guide compares the five flutes RMG exporters meet most often, so you can match the right one to your product.
What is a flute and what does it do?
A flute is the corrugated, wave-shaped paper medium glued between the two flat liners of a board. Those arches do the structural work: they resist crushing, keep the liners spaced apart and absorb shock. Change the size and pitch of the arches and you change everything about the board — its thickness, how much it cushions, how well it stacks and how smoothly it prints. Flutes are labelled with letters (A, B, C, E) that were assigned in the order they were invented, not by size, which is why the sizes do not run in alphabetical order.
E flute — fine, printable, retail-ready
At roughly 1.5 mm thick, E flute is the thinnest of the common profiles. Its tight, dense wave gives a smooth, flat surface that takes high-quality print and crisp die-cutting, which makes it the go-to for printed retail boxes, gift packaging and inner cartons. E flute protects the product and looks sharp on a shelf, but it is not built for heavy stacking — keep it for lighter, presentation-led packaging.
B flute — puncture-resistant printed boxes
At about 3 mm, B flute has a higher number of shorter arches per metre, giving good crush and puncture resistance and a flat enough surface for solid print. It is a versatile middle ground — common for printed shipping boxes, point-of-sale displays and product boxes that need more toughness than E flute offers without the extra thickness of taller profiles.
C flute — common in the industry (we run A, B and E)
At roughly 4 mm, C flute is a profile you will meet in many buyer manuals. Its taller arches give good stacking strength and cushioning. Padma does not run C flute — our corrugators produce A, B and E. Where a callout asks for C, we match the required burst and ECT with B flute or A flute board, and our default recommendation when a buyer has no specific requirement is B flute.
A flute — maximum cushioning
A flute is the tallest single-wall profile at around 5 mm, with the largest arches and the most air space. That gives it the greatest cushioning and vertical compression resistance of the single-wall flutes, useful for fragile or lightweight bulky goods. It adds thickness versus B flute, but it is the strongest single-wall profile we run and the right step before moving to double-wall.
AB double-wall — heavy and high-stack shipments
AB glues an A flute and a B flute together into a single double-wall board roughly 8 mm thick. The result is a big jump in strength, rigidity and cushioning — the right choice for heavy contents, tall pallet stacks and long sea voyages where a single-wall carton would crush. You pay for it in board cost and a slightly rougher print surface, so reserve double-wall for shipments that genuinely need it. Our bursting strength vs ECT guide helps you confirm whether single or double-wall is required.
How do I choose the right flute?
Match the flute to the job: E for printed retail and inners, B for tougher printed boxes and standard export master cartons, A for extra cushioning, and AB double-wall for heavy or high-stack loads. Then confirm the choice against your real product weight, stack height and transit mode rather than guessing. Read our companion guides on board grades and GSM and choosing the right export carton, or jump straight to the free packaging calculators for an indicative spec.
Flute type FAQs
What is a flute in corrugated board?
A flute is the wavy paper medium running between the liners of a corrugated board. Its arched shape resists crushing and keeps the liners apart, giving the board rigidity and cushioning. The flute profile — A, B, C, E or a double-wall combination — determines the board's thickness and how it performs.
Which flute is best for export master cartons?
In our range, B flute (about 3 mm) is the all-round choice for export master cartons — it balances stacking strength, print surface and economy. For heavy or high-stack loads, A flute or AB double-wall adds extra protection.
What flute should I use for printed retail boxes?
E flute (around 1.5 mm) is the usual choice for printed retail and inner boxes. Its thin, dense profile gives a smooth, flat surface for high-quality print and die-cutting while still protecting the product. B flute is a good step up when a retail box also needs more puncture resistance.
What is AB double-wall flute used for?
Double-wall glues two flutes into one board for heavy contents, tall pallet stacks and long sea transit where a single-wall box would crush. Our double-wall is AB — an A flute and a B flute combined, roughly 8 mm thick — trading a little print smoothness for much greater strength.
Need help picking a flute?
Tell us your product, weight and transit mode — we'll recommend a flute and quote within 24 hours.