could be a heavier manila paper weight to make the envelope stronger. used it to send out calendars and they had binding combs and concern about it breaking out of the envelope. they didn't whew!
I SELL CHILDRENS BOOKS~~THIS IS A GREAT QUALITY ENVELOPE I WILL USE FOR YEARS TO COME~ ONLY THING I WISH THEY HAD A SALE OF BUY SEVERAL GET A DEAL~NOT EVER DEALS ON THESE FOR ME AND IN THIS TIME OF ECONOMICS HAS FORCED ME TO SOMETIMES WRAP MY OWN BOOKS IN BROWN BAGS AND MY OWN WRAPPING IF MY FUNDS WON'T ALLOW ME EXTRA THAT MONTH TO GET MORE ENVELOPES