4 x 6 Flyers also called 4 x 6 Postcards are by far the most popular size of all. Our 4 x 6 flyers are double-sided printed on 12PT glossy card stock with UV Gloss coating. Only have a one-side? That is fine. Just choose that in the options so the UV coating will be omitted on the back so that you can easily write important info on the back. The flyer will print at about 4×6 and trimmed down from there.