The envelope is well built. It is sturdy. The edges are sealed well. The glue on these particular envelopes works very well. And the size of the envelope allows you to stay within letter size US postal dimension constraints provided you stay within weight limits as well.
This is a good choice for sturdy envelopes in this size. The flap adhesive seems fine but since we seal using packing tape this is not a concern. The price makes this an economical choice.
Buy the self seal a little more money but better constructed. The bottom flap ends are not glued so you have to tape them down the corners and sometimes the whole lick strip don't seal. If it's interoffice not going through the postal system it should be fine. If you have documents be sure to have the tape handy because it's the only way the corners and flaps will stay down.