Oct 13, 2026Help Center
Corrugated Flutes Explained: E, B, C and BC for Custom Boxes
E, B, C, F and BC flute profiles change how a corrugated box stacks, cushions and prints. A plain-English guide to picking the right flute for your product.
What a flute actually is
Corrugated board is a sandwich: two flat liner papers with a wavy layer — the flute — glued between them. The flute is what gives corrugated boxes their strength-to-weight ratio and cushioning. Change the flute and you change how the box stacks, absorbs shock and prints.
The four profiles you will actually meet
- F flute — about 0.8 mm thick. Very fine, takes crisp printing; used for small retail packaging and die-cut inserts.
- E flute — about 1.5 mm. The default for custom mailer boxes and retail packaging: good print surface, decent protection, slim profile.
- B flute — about 3 mm. Thicker cushioning; common for die-cut mailers, partitions and inner packaging.
- C flute — about 4 mm. The standard shipping box flute; a good balance of stacking strength and cost.
Need heavier duty? BC double wall combines a B and a C flute for export cartons and heavy retail-ready packaging.
Which flute fits your product
- Light e-commerce goods and branded unboxing: E flute custom mailer boxes.
- Subscription and fragile items that need inner fitments: B flute with die-cut inserts.
- Heavier retail or export shipments: C flute or BC double wall RSC slotted cartons.
Flute and print quality
The finer the flute, the flatter the printing surface. E and F flute take offset-quality printing and fine text; direct printing on C flute shows more flute shadow, so keep artwork bold. If you need photographic print on a strong box, consider litho-lamination: print on SBS paper, laminate to corrugated.
The takeaway
Choose the flute by weight, fragility and print ambition — not habit. Tell your supplier the product weight and how it ships, and ask which flute they recommend. Not sure? Send us your product details and we will spec the board for you, free of charge.