SIZE: You have two circles with dots that are the size that is written along the outside of the circle. There is a dark circle and a light one. Decide which one to use depending on the color of the sand. Sprinkle a little sand on the paper and find the size that the particles fit into. In most cases there will be a range of sizes. Size just tells you how long a particle has been eroding in the system. The longer it has been moving in the system, the particle will be generally smaller.