There are four different strengths.
LightGrip: The blue mat is best for printer paper, thin cardstock, construction paper, and regular vinyl.
StandardGrip: The green mat is best for medium materials such as cardstock, heat transfer vinyl, permanent or removable vinyl, bonded fabric, and textured paper.
StrongGrip: The purple mat is for heavy materials such as thick and glitter cardstock, wood, chipboard, leather, and poster board.
FabricGrip: The pink mat is best for bonded fabric or materials with any fabric on it with the rotary blade and Cricut maker.
If you want to make Joy Cards, you might want to check out the unique Card Mat, which has a divider to protect the backs of folded cards. Otherwise, you can use LightGrip or StandardGrip.