What Is Flute?
Updated · Vorex Packaging
A flute is the wavy middle layer of corrugated board, glued between flat liners to make the board stiff and cushioning. Flutes come in standard sizes named by letter, such as A, B, C, E and F, and the flute size decides the board's thickness, strength, cushioning and how smoothly it prints.
Corrugated board is built like a sandwich: a fluted paper, called the medium, sits between two flat liner sheets. The arches of the flute act like small columns that resist crushing and cushion the contents.
Common flute sizes
- C-flute: a thick, widely used flute for general shipping cartons.
- B-flute: about 1/8 inch, good puncture resistance and stacking strength.
- E-flute: about 1/16 inch, a smooth surface for printed mailers.
- F-flute: even finer, used for small retail boxes.
- Double-wall (such as BC): two flute layers for heavy loads.
How to choose
Larger flutes protect more but print less sharply and take more space. Smaller flutes look cleaner and fold neatly but protect less. Choose by product weight, fragility, shipping method and how important the printed surface is.
