What is "kubotan"

Kubotan (sometimes erroneously spelled as Kubaton or Kobutan) is a genericized trademark for a self-defense keychain weapon developed by Sōke Takayuki Kubota in the late 1960s. It is typically no more than 5.5 inches (14 centimetres) long and about half an inch (1.25 centimetres) in diameter, slightly thicker or the same size as a marker pen. The material is usually of a hard high-impact plastic (e.g. Lexan). The body of the Kubotan is lined with six round grooves with a screw eye and/or swivel and split ring attachment at one end for keys.