These minicards are called Sraplings. The size is 8,5" x 1,5" or 21,6 x 3,8 cm. (fold them before stamping). I discovered this size recently and it's such a fun size to work with. I kept mine very plain and simple. They make wonderful giftcards.
These are the Stampotique stamps I used:
Word collage 7155
Have a wonderful and creative day!