Where can I buy the most cost effective bubble shipping envelopes. Man, do they range in price. I've go to Uline, and a 8.5x12 was 19 cents. Someone told me they found them for as little as .12 cents. Also, what does the #0, #1, #2, #3 mean on the envelopes? I'm guessing it is the weight of the envelopes. Is there a typical standard # for mailing small items? When is it better to ship in a box?