german made  spring loaded 3  cam locking tumblers act like a sprague clutch and grip any shank between size of 8 mm to 13 mm-5/16-1/2 in  just grip shiny barrell and  turn cw to open jaws insert shank release and shank held in death grip by sprauge action reverse procedure for quick release fast acting  1/4 turn  very clever hardened in excellent condt