The KOGA SD1 is a highly effective self defense tool made of virtually unbreakable plastic. It was designed by the world renowned martial artist and law enforcement trainer, Bob Koga. With proper training, it will function as a fantastic aid in obtaining joint locks and submission holds. It can also be used to target pressure points or act as an impact tool. Black, Silent and Undetectable Made of Virtually Unbreakable Plastic Only Weighs 4.1 oz.