Okw com knobs with recess blackgrey 16 50mm okw a 30 31 069 this okw a 30 31 069 com knob 31mm black has a modern design with several excellent features including a brass collet with parallel through hole and lock nut on the top for tight fitting to a control spindle this contemporary knob is also suitable for fitting accessory nut covers pointers discs and dials along with a slot for arrow marking elements okw a 30 31 069 com knob w slot 31mm bore 6mm height 16mm nero b