The Rainbow Pebbles Classroom Set is a construction and early mathematics manipulative, and is ideal for developing fine motor skills, and for counting, sorting and creative design activities. Size range of pebbles: 3.4"L x 2.1"W - 1.1"L x 0.75"W. Size of activity cards: 11.7"L x 8.25"W (large) and 6.8"L x 4.5"W (small).