Home › Blog › Flute & Board Strength Guide: B vs. C vs. E vs. Double-Wall
Buyer GuidesFlute & Board Strength Guide: B vs. C vs. E vs. Double-Wall
The flute is the fluted, wavy layer inside a corrugated board, and it is the single most important structural choice you’ll make — it determines whether the box crushes under a stack or arrives square. The common single-wall flutes (E, B, and C) and double-wall (BC) each fit a different weight and print job.
Here’s how to match the flute and board strength to the product.
E and B flute for light goods and print
E flute is thin with a fine profile, so it prints crisply and suits small, light retail and e-commerce boxes. B flute is a bit thicker with good crush resistance, the versatile default for mailers and lighter shippers. Both are single-wall and economical.
C flute for standard shipping
C flute is thicker than B with more cushioning and stacking strength, which makes it the workhorse for standard RSC shipping cartons carrying moderate weight. It’s the most common single-wall shipping board for good reason.
Double-wall for heavy and fragile freight
BC double-wall bonds a B and a C flute for maximum stacking strength and puncture resistance — the board for heavy, dense, or fragile freight that must survive palletized stacking and a long haul. It costs more but prevents costly damage claims.
| Flute | Profile | Best for |
|---|---|---|
| E flute | Thin, fine, crisp print | Small, light retail boxes |
| B flute | Medium, crush-resistant | Mailers, light shippers |
| C flute | Thicker, more cushion | Standard shipping cartons |
| BC double-wall | Two flutes, strongest | Heavy & fragile freight |
Rule of thumb: match the flute to weight and stacking, not price — under-specced board that crushes costs far more in damage than the board upgrade would have.
Tell us your product weight and how it stacks and we’ll spec the flute, ECT, and burst strength — free, within one business day.