Even though Tyvek, in this size envelope, is not a common sight for the average person, they will
last.
PLEASE NOTE: These are the envelopes, NOT the Himber envelopes!
HOWEVER - if you have
the Osterland method of making a double envelope, you can make a Himber envelope out of two of these
envelopes using a strong glue stick and basic arts and crafts.
You can even make an envelope
with a flap on each side that will look like the Tyvek Himber you buy but, I think, even better than
the bought one.
The Osterland book is "Diverse Deceptions".