These blank index cards are made of the highest quality 14pt paper. These postcards are great for taking notes, making flash cards, making your own mail-able postcard, and many more methods. The index cards are unlined and are blank on both sides. Each pack comes with a bundle of 50 postcards. These cards are uncoated which means you can use the following to write on with no problems: Pens (gel, ball point, etc.), pencils, permanent markers, highlighters, ink stamps, markers, colored pencils, and many more. There are so many possibilities that they all can't be listed.