The shell dressings were originally issued to medics to carry in the shell dressing bags.
Latter in the war, when a larger bandage was need by the individual soldiers, they could be seen carried tied to the shoulder strap of their webbing or under the net of their helmet.
This replica shell dressing is made just like the original with a cotton outer with tie tabs. Inside is a waterproof fabric covered bandage, the waterproof cover could be opened to cover a wound keeping it dry. The cotton wool bandage has long ties to wrap around the limb keeping the pressure on the wound.