I found that when mailing, if you fold the material so that it's almost the same size as the envelope it mails better. I know with some of the envelopes I received were fine, but it the material was folded thick and smaller than the envelope the machine left skid marks on them and postage due was added before I received it. Mailing out the finished blocks can be just as bad at a fussy post office-Last swap I had envelopes go for $.44 to $1.74 because of the thickness of the seams. Towards the end of the swap I was much more attenative to the seams and the blocks went out for $.64 and I did use larger envelopes! It also depends on who's at the counter, some clerks are better at letting things go through. :lol: But the big difference in price was because of the thickness (not just a letter inside)-or so the clerk explained to me-I sent 6 at $1.74 ea. that was a shock, but then I changed the size of the envelope and had no other high postage. 8-) I just put it up to trial and error!