The Tunkuwa (トンファー) is more known by its chinese name  Tonfa.
The Tonfa is still used by numerous police forces around the World.
Tunkuwa was originaly handle of a millstone used for grinding grain.  Tonfa is manufactured in red oak and its size dépends of forearm length.
Tonfa allows powerful blocks and counter-attacks. It is great complement to Karate-Do by improving punch techniques and strength.

Katas (カタ) :

Tunkawa Kihin Ichi
Matayoshi no Tunkuwa dai ichi
Matayoshi no Tunkuwa dai ni

 

Here is below the basic Tonfa kata  Tunkuwa Kihon Ichi :