Most postcards are printed on 100# Cover Gloss or Smooth. This heavy card stock is common for business cards, postcards and book covers. If you want something sturdier, we recommend the 16-pt Extra Thick Cover. Another great option for postcards with bright graphics or photos is the 12-pt C1S. This is a sturdy card stock with a high-gloss finish on one side, and an uncoated surface on the other (so it can be written on).