The Kusari-Fundu consists of a chain, almost an arms length, and two small weights, one on each end.
It can almost be considered an assassin's tool, due to the various multitude of choke- and strangleholds for which it can be used.

The Kusuri-Fundu is also a superb weapon for grappling and striking.
It is a diverse tool which can be used in a similar fashion to nearly any other tool.