white acid-free mat with foamcore backing - ships flat in a box
Pros of shipping in a tube: cheaper, less likely to get damaged during shipping, and you get to pick your own mat style and color; pros of shipping matted: you don't have to deal with matting, you only have to get a frame, and as a bonus, front of the mat is signed. Keep in mind most retail 16"x20" frames come with an 11"x14" mat included.
