Printed labels are the minimum requirement these days, even for free shipping. I prefer envelopes over larger packages. Maybe I'm wrong, but I just think they are safer. It's the most common type of parcel, so it blends into a much larger crowd. I also think an envelope is much less likely to be pulled out and inspected. They want to bust big drug shipments. Of course, envelopes only work for small orders, which is fine by me.