AKAR A4/C4-234x334mm -[ Pack of 50 ] Strong Rigid Cardboard Envelopes/Cardboard C4 Envelope, Heavy Duty 400gsm,Corrugated Capacity Book Mailers,Peel & Seal, Rip & Strip Open Capacity A4 Book Mailler

They seem relatively sturdy, and the price is good for the amount you get, but they don't expand as much as you'd maybe want them to, as once you put something that generally fills the envelope but is deeper than about 1.5cm in there, the seal that folds over the top doesn't quite reach all the way and it also leaves gaps open at the corners. I was trying to use them for text books that were about 2.5cm thick.Maybe a simple longer folding edge would solve this and make them more practical for a wider variety of sized items to go into them. The ones that the likes of amazon use always seem to fold down to maybe a third of the way down the envelope rather than just folding down a cm or two.Otherwise I'm back to the book fold style packaging, which is a bit bulky and a bit expensive, and is often too big for what I'm sending.But on the plus side, if you are sending things that are under 1.5cm thick, then these are generally brilliant.

These are very strong and sturdy more so than other rigid envelopes I have used. Another bonus is they cost less to send in the post.

I'm using them to post my artwork. They're much sturdier than any I found in the post office or rymans and the adhesive strip holds really well.

Good value and quality envelopes that help to post larger 'soft' items as royal mail large letters and not small parcels.A bit costly as a business solution, but hopefully customers will recycle them.Only slight down side is that they don't always stick very well, but as said I was effectively over packing them so not fully there fault.

These would be perfect for posting prints if they have not been bent in the middle! Only after using a half of the pack, I noticed that the other half is absolutely useless. Do not recommend, a waste of money!

They are not as sturdy as more expensive ones and wouldn't protect your books well. However, they are excellent value for money.

These are great! So much sturdier than the other sellers on Instagram, which I’ve tried and had to return! I’ve ordered these envelopes multiple times. We did have a slight problem with the corners of the envelope ripping when we closed them on one batch but the seller swiftly rectified the situation. Speedy delivery too! Thanks

Not bad for the price, however I had to tape along the edges as it tear along the top. The adhesive isn’t very good either, but overall it works well for what I need it for (posting notepads).