SIZING YOUR DUALLY:
Most riding breeds will fit this size as adults. For standard horses from 600 to 1250 pounds as well as large ponies, e.g. Icelandic or Hackneys.
Nose – Minimum 23 in (58,4 cm), Maximum 31 in (78,7 cm)
Head – Minimum 37 in (94 cm), Maximum 45 in (114,3 cm)
Cheek – From Ring Ring 8 in (20,3 cm)
The size of the head matters more in fitting a Dually than the weight of the horse.