The bonding part of the upper cover is provided with anti-disassembly lines composed of intermittent tear lines.  

At the edges is a three-step corn glue that will not come out of place even at high temperatures. 

It is difficult to open letters easily after they are sealed and sealed;  If the upper cover is forcibly removed illegally, it will leave a tear mark on the anti-tear marks and around it, even if it is re-sealed, it will leave a mark.  

Protect the recipient's personal information security, especially for bank credit card business and credit securities and other related industries.