Trying to figure out halter sizes for horses is like trying to figure out the right size for a new pair of jeans. Every manufacturer seems to have their own idea of what "Horse," "Cob," "Pony," and so on, mean. The video and diagrams below should help you accurately determine what size GG Halter your equine needs.
Once you've figured it out, select the halter you'd like:
Halter Sizing Tutorial Video
GG Halter Sizing Charts