Species of Naja or "cobras" are snakes that can grow up to 1.9 m long or, in a few species, up to 3.1m long. When threatened, they can raise up their front portion and flatten their necks, thereby presenting a larger appearance to a potential predator. All species produce a neurotoxic venom. Some species inject it through their front fangs; others squirt it out through a rifled opening in their fangs. The latter group are often called "spitting" cobras.