Under 38" is miniature...A and B size.
Miniature donkeys are native to the Mediterranian islands of Sicily and Sardinia. It is difficult to import them now because 1) The quality of donkey left in Sicily and Sardinia is not good, and, 2) It is very difficult to pass the tests given by quarantine stations at the Dept. of Agriculture. However, this writer purchased two donkeys imported into this country from Sicily some time ago so the task is not impossible, just improbable. Miniature Donkeys have not been bred down in size per se. The 25-30 Miniature Donkeys originally imported into the U.S. were between the sizes of 32" and 38" with the majority of them being in the 35"-37" size range. Over the years, breeders have concentrated more on the 32"-33" size and today your most desirable and well-conformed donkeys are from 31" to 35". The word "miniature" usually connotates animals that have been bred-down in size, so keep in mind that 'miniature donkeys' are simply diminutive and not bred down such is the case of many other 'miniature' animals.