Mules come in every size and shape imaginable. Miniature mules (even to under 36") can be seen all the way up to 17 hand Percheron draft (by Mammoth Jacks) Mules. The Poitou donkey was used exclusively for breeding huge draft mules from a breed of draft horse called the Mullasier - the Mule producer. The build of the mule is a combination of both parents. The head resembles both, the eyes being more almond-shaped (inherited from the D-shaped eye socket of the donkey). Male mules may have more prominent brow ridges like those of most donkey jacks. The neck is straight and has little arch, even in mules from Arab or Warmblood mares. The overall body shape will be dependent on the conformation of both parents. Due to hybrid vigor, the mule has the possibility of growing taller than either parent.