Posted by Marty Boyer on

Understanding the importance of how little ridges (or flutes) make a big impact on shipment security when it comes to your packages.

Understanding flutes and boxes

  • Flutes are the “S”-shaped waves or arches that compose each board in a box. Collectively, these are called the corrugation of the boards.
  • Flutes determine how resistant a box is to damage and the height they can be stacked for shipping.
  • Flutes come in five different letter grades – A, B, C, E and F – related to their thickness of their profile 


While the word may cause the public to think of the musical instrument, flutes have an entirely different meaning when it comes to boxes as they are the “S”-shaped waves/arches that compose a box’s corrugation. Flutes are important because they determine a box’s strength, cushioning and reinforcement that make up each side’s board.

Flutes typically consist of five different sizes, each of which is identified by one of five letters: A, B, C, E and F. Each letter corresponds to the thickness of the flute’s profile, with A being the strongest on down to F. Flutes are what help boxes prevent damage by resisting pressure applied from various angles with the open space between the flutes providing both cushioning and insulation in the event of temperature changes as it travels.

By the letters:

  • A Flute is the strongest of all, at one-fourth of an inch in height.
  • B Flute is about one-eighth of an inch in height.
  • C Flute is typically good for printing and is about eleven sixth fourths of an inch (4 millimeters) in height and is also the most common all-purpose flute.
  • E Flutes are one-sixteenth of an inch height; pizza boxes are typically E flutes.
  • F Flutes are one-thirty second (0.8 millimeters) of an inch in height; a fast-food hamburger box is a typical use of F flutes.


Chart Explaining Cardboard Flutes


In addition to flute type, you’ll want to determine the right strength needed of the boards of the box you intend to use. There are four primary board types: 

  • A single face board only has two layers – a linear layer and a corrugated layer. It’s typically used inside of boxes to add extra cushioning since it is not as durable as other corrugated boards.
  • A single wall board is the most common type of corrugated cardboard, consisting of two outer liners and a middle layer of corrugation.
  • A double wall board has two layers of corrugated fluting wedged in among three liners (think of a sandwich with the liners being the buns and meat in the middle of two layers of toppings above and below)
    • A triple wall board is composed of two sets of a liner on top of luting on top of another liner and are the strongest of all.

The key to picking out the right flute and board combination, of course, is knowing (1) What you need to ship and (2) Just how secure it needs to be. Whereas using a heavier box with sturdy boards might be a bit of overkill for an item that’s relatively stable, using a box with flutes that aren’t strong enough can result in damage – and subsequently, unhappy customers – to a fragile or heavy item.

If you are in the market for custom corrugated pads, you’ll want to be sure to specify how you want the fluting to be oriented in your customized pad. Fluting is going to provide the most strength when used parallel to the fluting orientation. While that might sound a little more technical, just know to ask about how the fluting will be oriented when ordering a custom pad. That is why we are here to help!

Have questions about what packaging or boxes might best serve your shipping needs? Just shoot us an email at info@3Dcorrugated.com or give us a call at (513) 241-8126 and we’ll help you find the perfect solution.

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