There is nothing wrong with corrugated mailers as long as one is selective as to what is placed in them, and how the envelope is marked. These corrugated mailers are much cheaper to mail than are bubble mailers. If corrugated mailers are used for mailing tokens or durable metal center chips, they are fine. If the outter envelope is marked "non-machineable" it does not go through the sorting machinery and the postage cost is only. 20 cents above the actual postage costs. A letter envelope with a corrugated mailer up to one-ounce cost only .66 cents to mail vs. over $2 to mail a bubble mailer because all bubble mailers are considered to be packages.