We receive a lot of parcel mail sent to us using US Postal Service flat rate boxes. Specifically, the small size box. That’s big enough to hold pretty much anything anyone needs to send to us, and often that stuff is pretty lightweight. Also, the flat rate boxes are actually free if you use the flat rate service.
Unfortunately, we tend to receive these flat rate boxes with standard postage paid instead of the flat rate. The flat rate for the small box is around $9, but we’ve seen people pay postage upwards of $22 to send a flat rate box with a few pieces of paper in it and a tiny widget.
If you are sending anything under a pound weight and can fit in a small flat rate box, be sure that you pay for the flat rate service and not standard postage rates.