The mat is a white mat that goes on top of the die and fabric before you run it through the Go. You have to have one and it sells separately from the dies. You get the size mat for the size die, usually two sizes will fit all of them except the strip dies, they are long. Check and see if one comes with your purchase. Usually the Go comes with a starter die and mat. I like the tumbler die, hst dies, and strip dies the most. I have about worn out my rag die, I make one complete block at a time with it. I have made over a dozen rag quilts, I can make one in a few hours. I'm thinking of getting the Studio but if my DD gets one first I'll use hers.