Freeform pieces come in precision-cut 2-cm. increments (2, 4, 6, 8 and 10 cm.) with large 2 cm. disks and bridges to support successful building and early math and metric system learning. Diameter of blocks varies. Typical set includes "Y" or forked pieces. We lovingly finish each unique set with flax oil. Tree Blocks come in a colorful, cotton twill, drawstring sack with attractive logo block. Ages 3 to adult. Safe, lab tested. Conforms to CPSC & ASTM 963- F, and EN 71. The standard measure of maple unit blocks (regular kids wooden blocks) is 3/4", virtually the same as 2 cm. The sets can be combined flawlessly.