A piece of Australian head wear was the side cap.
Militia units wore this cap, and this design of cap had service in the British and Australian armies for many years.

This envelope type cap did not vary much in the many years it saw service. The cap had a brow piece that could be folded down to protect the forehead in cold weather, as well as side curtains that could be lowered also to protect the ears and neck. There are two buttons at the front of these curtains, which can be done up to add to the protection of the face and mouth as well. This cap could be worn under a helmet. This early version of the cap is made of a particularly fine wool, almost like a doeskin wool, and is in a light green shade. These caps can be worn with a chin strap, which attaches to two small metal hooks on the body of the hat. When this hat is worn, it is not worn with the centre of the hat to the centre of the head, but to above the right eye. The chin strap hooks are therefore not fixed isometrically but are offset to allow the hat to be worn at an angle and allow the chinstrap to be worn squarely on the face.

This Australian cap varies slightly from the
British version, by being made of a better quality wool and being slightly higher at the front.

These hats were worn throughout the First World War by Australians, and are often seen in photos from the Gallipoli campaign in 1915. The Australian Flying Corps seemed to use a lot of this type of hat, as a more serviceable item around windy airplanes. It is expected that most of those caps were supplied by the British, as they are found with British makers marks.