Understanding Corrugated Flutes

E Flute, B Flute, C Flute, A Flute Corrugated Material

At a Glance

  • Corrugated material is available in different wall thicknesses, known as flutes sizes
  • A-Flute is 1/4 inch thick, greatest cushioning for fragile products
  • C-Flute 3/16 inch thick, commonly used for shipping cases
  • B-Flute is 1/8 inch thick, flatter surface for higher quality printing and die cutting
  • E-Flute is 1/16 inch thick, a strong alternative for paperboard folding cartons
Sustainability Tip

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Different Corrugate Thicknesses for Different Uses

Corrugated material is available in different wall thicknesses, known as flutes sizes. Each flute size has a particularly useful function, from shipping strength to reducing storage space to improved printability. Here are descriptions and details of each corrugated flute size.

Corrugated material is comprised of three fiberboard layers; two linerboards sandwich a middle sheet that is in a wave-shaped a pattern of arches known as flutes. These flutes are anchored to the linerboard with an adhesive.

On end, flutes form rigid columns, capable of supporting a great deal of weight. From the side of the board, the space between the flutes acts as a cushion to protect the container's contents. Flutes also serve as an insulator, providing protection from sudden temperature changes. The linerboard provides additional strength and protects the flutes from damage.

Flutes A to F

Flutes come in sizes, known as flute profiles, ranging from A-flute (the largest) to F-flute and below (microflutes). The letter designation relates to the order that the flutes were invented, not the relative sizes.

Larger flute profiles deliver greater vertical compression strength and cushioning. Smaller flute profiles provide enhanced structural and printing capabilities for retail packaging.

E-Flute: 1/16" thick, 90 flutes per linear foot
B-Flute: 1/8" thick, 47 flutes per linear foot
C-Flute: 3/16" thick, 39 flutes per linear foot
A-Flute: 1/4" thick, 33 flutes per linear foot


A-flute is the original corrugated flute design and is the thickest. With it's thickness , A-flute provides the greatest cushioning properties for fragile products. Because A-flute offers excellent stiffness qualities and short column crush resistance, it has application across a broad range of customer uses.

Flutes per Linear Foot: 33
Thickness: 1/4"


C-flute is the most widely used flute size, commonly used for shipping cases. Often used for packaging glass products, dairy products, and furniture, C-flute offers good crushing resistance, good stacking strength, and highly acceptable printing properties. Very common, roughly 80% of corrugated containers are made of C-flute board.

Flutes per Linear Foot: 39
Thickness: 3/16"


With lower arch heights and more flutes per foot than A-flute material, B-flute contacts liners at a greater number of points. This additional support provides a stiff, flat surface for high quality printing and die cutting. B-flute offers excellent puncture and crush resistant properties, and consumes less warehouse space. Developed for packaging canned goods, B-flute is used for beverage trays, wrap-around blanks, glass-to-glass packs, and slipsheets. B-flute is also preferred for high speed, automatic packing lines as well as for pads, dividers, partitions, and other forms of inner packing.

Flutes per Linear Foot: 47
Thickness: 1/8"


Containing about 90 flutes per foot, E-flute has greater crush resistance and a relatively flat surface for high quality printing applications. The thin board profile of E-flute reduces outer box dimensions, and can help save storage space. Because of its thin profile, cushioning properties, and flat surface, E-flute offers a strong alternative for conventional paperboard folding cartons including boxes for cosmetics, fragile glass, and ceramic items, and delicate instruments.

Flutes per Linear Foot: 90
Thickness: 1/16"


Developed for small retail packaging, F-flute makes packages with lower fiber content. With reduced fiber in the packaging, a more rigid box is created with less solid waste going into landfills. In Europe, F-flute is being used for specialty packaging, point-of-purchase displays, jewelry and cosmetic packages, and shoe boxes. In the United States, fast food chains are adopting F-fLute material in clamshell packaging.

Flutes per Linear Foot: 125
Thickness: 1/32"

Please contact Pro Pac or call 888-318-0083 for your corrugated shipping cases.

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