I accidentally purchased this and used 1-2 sheets. The one sheet I used was smooth, so I think it's a thin sheet of paper to prevent ink from sticking. I'm leaving it as is because replacing it would likely crease the inner sheets. This item did not originally come with cardboard. I will reinforce it and take measures to prevent folding during shipping. Single-sided, for crafts, art, printmaking, transfer, copying, and copy paper.