Sirio Ultra Black Cardstock is the best black cardstock on the market! This high-quality cardstock is produced in Italy and the exceptional quality makes a noticeable difference. ...Sirio Ultra Black Cardstock is a deep, dense, black cardstock that has color all the way through, so you won't get white edges when torn or cut. In fact, it's the most intense black cardstock on the market. The heavier weight gives added stability to projects and the deep, rich black makes all the other colors pop against it. .