Experts believe that you must be able to hold the Shohin tree in one hand, indicating the exact measure of the height of the tree is not strictly important. Mame Bonsai trees are even smaller; under 4" (10cm) tall.
Shohin, Mame and Bonsai compared
Shohin and Mame are quite similar to Bonsai, but besides size, differences can also be distinguished in its care guidelines. As pots get smaller more regular watering and fertilizing is required. Another difference can be found in the amount of detail depicted by the trees. Real trees have thousands of leaves and branches, but as size decreases, all the way to the tiny little Mame trees, detail tends to decrease as well. Therefore, Shohin and especially Mame can be thought of as being more idealistic.
Read the article "what is Bonsai" for more insights in size classifications.