Expandable and tamper evident for secure mailing
Brown cardboard envelopes with locking flaps are a tamper proof envelope for posting flat media and documents. Once the flap is inserted it cannot be opened without clear damage to the board, so any interference shows. The 350gsm micro-flute corrugated board keeps contents flat and free from creasing, and reinforced corners guard against knocks. Expandable edges let the tamper proof envelope increase in height by up to 40mm, so one format posts DVDs, CDs, books, catalogues and calendars. Available in a range of sizes from 330 x 230mm up to 670 x 520mm (opening width x internal height) covering large letter, small parcel, medium parcel and large parcel mail formats. For higher-value contents, the closure can be double sealed with packaging tape.
Sold and priced per pack.
Where do tamper proof envelopes work best?
Tamper proof envelopes suit posting flat media and documents that must stay rigid and show clear evidence of any interference.
- Books, catalogues and calendars, where 350gsm micro-flute board keeps contents flat and reduces creasing in transit.
- CDs and DVDs, where reinforced corners add protection against knocks during handling.
- Mixed-depth e-commerce orders, where expandable edges raise the height up to 40mm across slim product profiles.
- Documents needing visible interference control, where locking flaps cannot be opened without clear damage to the board.
Not for
- Liquids, powders or loose-fill goods. Use a sealed inner bag or pouch before any outer pack.
- Fragile items needing all-round cushioning, such as glassware or ceramics. Use cardboard boxes with void fill.
- Items deeper than 40mm. Use a postal box for greater depth and side protection.
Specifications
- Colour: brown
- Material: 350gsm micro-flute corrugated board
- Security: tamper-evident locking flaps
- Corner protection: reinforced corners
- Expandable edges: increase height up to 40mm
- Sizes: five sizes from 330 x 230mm up to 670 x 520mm (opening width x internal height)
- Closure: locking flaps, can be double sealed with tape
- Suitable contents: DVDs, CDs, books, catalogues and calendars
Choose the right cardboard envelope
These tamper proof envelopes are ideal for when flat media need rigidity and visible tamper evidence.
- Choose cardboard tamper proof envelopes when you need a tamper proof envelope shows interference for books, media and documents.
- Choose cardboard mailing envelopes when you want the same board closed with a fast self-adhesive strip and pull-tab rather than a locking flap.
- Choose a rigid mailer when you want flat solid board with a short edge opening rather than corrugated expandable edges.
- Choose white cardboard envelopes when you want board protection in a white finish.
FAQs
Can these envelopes be opened without visible damage?
No. Opening the mailer after the flap locks causes clear damage to the board, so interference shows quickly.
Do they protect contents from bending?
These hard cardboard envelopes use 350gsm micro-flute corrugated board, which holds a rigid structure and keeps flat items crease-free in normal posting.
Can they hold products of different thicknesses?
Yes, within the limit. Expandable edges raise the height up to 40mm, so one format covers several slim profiles.
Should I tape the envelope as well as using the locking flap?
For extra security, double seal the closure with tape, especially for higher-value contents or longer journeys.
Also useful
- Cardboard envelopes for comparing locking-flap, adhesive-strip and solid-board formats.
- Labels for carrier routing on the flat outer face of each mailer.
- Postal tubes for larger prints, posters and blueprints that can be rolled up for postage.
Our product advice
How to choose the correct size brown cardboard envelope for your product:When the cardboard envelope is expanded, please note that envelope decreases in opening and length measurements.To use at minimum capacity: Subtract 20 mm from the opening and 10 mm from the length.To use at maximum capacity: Subtract 60 mm from the opening and 30 mm from the length.
