Kẹp/giá trưng bày Postcard siêu mỏng

I made this model to show my homemade postcards (for postcrossing) on local markets to sell. The idea is to attach this to a rod, 6 or 7 of the holders above eachother, to display cards. With the model with the holes, you can feed a string through it, and display your cards at home, on the wall. 

The holder fit any card up to 150mm. I use 300gsm watercolor paper and it fits great. I haven't tried anything thicker.