I checked on this too when I mailed back my first Downy quilt. I got the largest padded envelopes I could find at an office supply store. It cost me $9 and some change to mail. It would have cost a dollar more to use a flat rate box in the size I needed. You have to factor in the cost of the padded envelopes (which aren't cheap), but I still came out ahead, and it was easy to do. The ones I have are self-sealing--so no tape necessary.