Board Backed / Hard Back Envelopes
However you refer to them - board backed envelopes or hard back envelopes - the aim is the same: a strong, good-value envelope that helps important contents arrive flat and intact.
Defenda Packaging supplies popular standard sizes and less common formats, including envelopes designed around Royal Mail Letter and Large Letter limits. Custom sizes and designs can also be manufactured subject to minimum quantities.
Popular Defenda Envelope Sizes
| Size | Approx. Dimensions | Typical Use |
|---|---|---|
| C3 / A3 Heavy Duty | 457 x 324mm | A3 documents and oversized flat items |
| C4 / A4 | 324 x 229mm | A4 documents without folding |
| C4 / A4 Heavy Duty | 324 x 229mm | Extra protection for A4 mailings |
| C5 / A5 Plus | 241 x 178mm | Photographs, programmes and greeting cards |
| C5 PiP | 238 x 163mm | Designed around Standard Letter dimensions |
| C6 / A6 | Postcard formats | Postcards, stamps and small flat items |
Construction
Legacy Defenda envelopes used strong paper faces with rigid recycled board backs and peel-and-seal closures. Many were UK manufactured and printed with Please Do Not Bend in red. Separate stiffeners are available for selected sizes where extra rigidity is required.