Corrugated Box Construction: Ply, Flute and Board Grade
A corrugated box specification is a short list of terms — ply, flute, GSM, BF, bursting strength — and each one changes what the box can carry. Knowing what they mean is the fastest way to compare quotes and to tell a supplier what you actually need.
Liners and flutes
Corrugated board is built from two kinds of paper. Liners are the flat sheets on the outside and between walls. The medium is the paper formed into flutes — the wave that gives corrugated its name. Glued together, liners and flutes make a board that is stiff, light and cushioning, because the flutes hold the liners apart like a row of arches.
Ply: how many walls
Ply counts the paper layers in the board. Each fluted wall adds two layers — the medium and another liner — so board comes in odd numbers:
| Ply | Walls | Typical use |
|---|---|---|
| 3 ply | Single | Light goods, inner cartons, short local routes |
| 5 ply | Double | Most industrial loads and general engineering parts |
| 7 ply | Triple | Heavy castings, machinery parts, high pallet stacks |
| 9 ply | Quadruple | The heaviest loads and long export routes |
Flute: the shape of the wave
Flutes are graded by height. Taller flutes cushion and stack better; shorter flutes resist puncture and give a smoother print surface.
| Flute | Typical height | Strength |
|---|---|---|
| A | 4.5–5 mm | Most cushioning and top-to-bottom stacking strength |
| B | 2.5–3 mm | Puncture and crush resistance; a good print surface |
| C | 3.5–4 mm | The all-rounder between A and B |
| E | 1.1–1.6 mm | Thin and rigid; the finest print surface |
Multi-wall boards combine profiles — for example B and C flutes together in a 5 ply board — to balance stacking strength against puncture resistance.
Board grade, BF and bursting strength
- GSM is the weight of a paper in grams per square metre. Heavier papers make stronger board. Our board range runs from 120 to 250 GSM.
- BF — bursting factor — rates a kraft paper’s bursting strength relative to its weight. Kraft papers are bought by GSM and BF together.
- Bursting strength is measured on the finished board, in kg/cm²: the pressure it takes before it ruptures. It depends on the papers and the ply. Our boards reach up to 32 kg/cm².
On a specification, these three figures, with the ply and flute, describe the board completely enough for a buyer to compare quotes and check a delivery.
Box styles
The most common style is the regular slotted carton: one piece of board, slotted and creased, with flaps that meet in the middle at top and bottom. It is economical and quick to pack. Die-cut styles are cut to a custom outline for trays, folders, locking lids and fitted inserts. We make both, built to the product’s internal dimensions.
Corrugated boxes from Bakrol Bujrang
Himalaya Packaging makes corrugated boxes from 3 to 9 ply in A, B, C and E flute at 25, Gopinath Industrial Estate, Behind Pawan Estate, Bakrol Bujrang, Ahmedabad — manufacturing since 2012. The specification for each order is set from the load and the route, agreed in writing, and proven on a physical sample. We deliver across Ahmedabad and Gujarat and by road across India. See our corrugated boxes, our capabilities, or our Ahmedabad plant page.
The product behind this article
Corrugated Boxes
The workhorse range, specified to the load rather than sold off a standard size list.
3–7 ply
A/B/C/E flute
120–250 GSM
