Perceptual subitizing is quickly recognizing the cardinality of small groups without counting. Perceptual subitizing progresses into conceptual subitizing, where quantities of larger groups are determined by quickly subitizing and combining smaller groups (i.e. 3 groups of five items for the number 15, or 2 groups of 10 for the number 20). Conceptual subitizing progresses into supporting more advanced methods for addition, subtraction, multiplication, and division. Each die is ten-sided so students can generate numbers by recognizing patterns depicting zero to nine. Made of acrylic. Set of 6, 20mm dice.