Corrugated board, the material used to make shipping boxes and mailer boxes, is made from three things: two sheets of kraft liner and one layer of fluting. Kraft liner is virgin paper that’s resistant to tearing and moisture, and is used for the outer layers of corrugated board. And fluting is the wavy, corrugated paper layer that’s sandwiched between the two sheets of liner. It’s what makes corrugated board rigid, durable and stackable, and without it, corrugated board wouldn’t actually be corrugated.
Fluting comes in different sizes, which are referred to as “flute profiles”. Some profiles are made from a single layer of fluting, like E-flute and B-flute, whilst others are made from two layers of fluting, like EB-flute. Each has its merits and limits, which is why it’s important to know what each means for your corrugated packaging. E-flute, for example, is ideal for printing on because of its high number of flutes (individual waves) per foot. This creates a smooth surface that doesn’t distort images and other artwork when printed on. At the same time, it’s too thin for shipping large, heavy products. Understanding flute profiles allows you to balance trade-offs and choose the fluting that best meets your exact needs.
Here’s a breakdown of four flute profiles you need to know about.
E flute is one of the thinnest flute profiles with a thickness of 1.5-2.0mm. This may not sound durable, but E flute has a high number of flutes (90) per foot. This not only creates the ideal surface for printing but offers excellent crush resistance too. E flute is also easy to fold, and it’s this balance of printability, durability and usability that makes it common for e-commerce packaging. Sourceful’s mailer boxes, for example, use E flute. Whilst E flute performs well in smaller sized boxes, its crush resistance starts to decrease at larger sizes. So if you’re shipping something big or heavy, a thicker flute profile may be a better choice for your corrugated packaging.
B flute (2.5-3.5mm) is the most common flute profile for shipping boxes. As it’s thicker than E flute, it offers more cushioning and better puncture resistance, but it still has a smooth surface for printing on. This makes it a good, cost-effective alternative to E flute if you’re shipping slightly bigger products but don’t want to sacrifice too much print performance.
Where B flute does falter is shipping very heavy items. For this, you will need a double-walled flute profile (two layers of fluting combined) to give your product the most protection.
As the name suggests, EB-flute (4.5-5.5mm)combines E-flute and B-flute into a double-walled material. Whereas the B-flute in EB-flute optimises durability, the E-flute optimises print performance. This makes it approximately 35% stronger than B-flute alone whilst maintaining a smooth outer surface for you to print on.
This combination may sound perfect, but like with all flute profiles, there are trade-offs. As a double-walled material, EB-flute is too thick to use in smaller boxes, like mailer boxes. And since it’s two flute profiles combined, it uses much more material than single-walled fluting. In turn, it’s more expensive and less sustainable, with a carbon footprint up to 40% higher than B-flute*. If you need to optimise both print performance and protection, EB-flute is a good choice, but using it without a purpose can create unnecessary costs and emissions for your corrugated packaging.
*Calculated using Sourceful’s live carbon footprint data. Learn more
BC flute is another double-walled material, but this time combining B flute and C flute. It’s one of the thickest flute profiles (7.0-8.0mm), and as a result one of the most durable, offering great cushioning and stacking strength.
The downside is that both B flute and C flute are thick flute profiles with a low number of flutes per foot. Because of this, BC flute doesn’t have the same print performance as EB flute and instead focuses almost exclusively on maximising protection. This is great for sending heavy items or stacking shipping boxes, but may not be the best option if branding is your priority.
With Sourceful, you can choose your fluting as you create corrugated packaging online in real-time. For mailer boxes, E flute is the default option, but if you need something else, you can contact us to discuss creating a bespoke mailer box. For shipping boxes, you can choose between B flute, EB flute and BC flute, whichever works best for you.