The Baat Jaam Dao here are made in a very strong engineeringed plastic. That has a good combination of toughness, stiffness, and dimensional stability.
These butterfly swords are good for form traning, and for light combat training. They can spring slightly, which provides a snap-effect that may be useful in traning.
In wing tsun the butterfly knives are known as Baat Jaam Do. Named after the system’s form, literally ‘Eight Chopping/Slashing Knives’ in Cantonese.