How big are a tarantula's fangs?

Boa Constrictors have teeth that are comparatively small to their body size, because they mostly use them for gripping their prey before ingestion. Anywhere from a few millimetres to a centimetre would be a good estimate, depending on size. They don't actually kill their prey with their fangs like venemous snakes do, they kill their prey by strangling them with their body, so they don't need large fangs or teeth.