I have been using these little watercolor postcards for over a year and I liked them so much, I got some to sell!
 
These are made by Potentate and they are made with 300 gsm cold press watercolor paper.
 
They come in a cute little tin that would be great to store paints in once you're done with the post cards, but that's besides the point. Each tin contains 24 post cards!
 
24 postcards
Postcards are approximately 4x6 inches
300 gsm watercolor paper
Cute tin!