These eco-friendly Junior Rainbow Pebbles are made of natural Fiber Particulate Composite (FPC), which is an agricultural waste product from rice stems and rice husks. Each pebble has its own natural grain as a result. Use Rainbow Pebbles as a construction and early math manipulative. Ideal for ages 3+. Includes 36 Pebbles in 3 shapes and 6 colors, and 8 double-sided activity cards. Approximate sizes of pebbles: 2.75" L x 1.1" W, 2.2" L x 1.8" W and 1.5" L x 1.4" W.