We know how common it is for people to lose the tiny brass clicker and spring that go underneath the rail of your KC-02 to make the hop adjustment wheel click, so we've painstakingly disassembled several hundred of the "correct" type of pen to get these brass clickers with a tungsten-carbide ball end, and ordered a load of springs suitable for the job!
These replace parts #21 and #22 in your KC-02. Our Guillotine Rails include a set of these as standard.