BH5UQJ The standard QSL cards are made of the same material as the front, and white cardstock is usually preferred for writing on. However, if you are using coated cards such as glossy or matte film, you can request that the vendor apply the coating to only one side (the front). Because these coated cards are typically made with copperplate cardstock as a base, I find that Dutch white cardstock is slightly less suitable for writing on than standard Dutch white cardstock. Therefore, if you don't have any specific requirements, I recommend choosing a full sheet of Dutch white cardstock or ice white pearl cardstock.