Because the sai was used primarily for self-defense, it was taught as a separate martial arts style. The "traditional" sai kata practiced today are of relatively recent invention. Modern sai training uses rigid karate-like punches and strikes, but the sai is more effectively used by using slashing and cutting movements.
Rapid Rotation Baton
The old becomes new again.
The rapid rotation baton has two side handles that permit rapid and fluid grip changes. The batons are supposedly more effective as an extreme close quarter baton against grips, grabs, body holds, and ground defense than previous batons. It has recently been adopted by the Federal Bureau of Prisons for maximum custody use. The baton is used by many different agencies, primarily by agencies that use community policing, due to the baton's non-threatening carry position.
Notice the similarity between the rapid rotation baton and the sai.