Collet knobs are an excellent alternative to the grub screw type of securing system for knobs.
Commonly found in professional equipment, once tightened they do not let go!
Ex Wandel & Goltermann test equipment (now obsolete)
Grey/Green knob - shaped for easy finger control (high central section)
Dimensions: 23mm diameter x 15mm high
White recessed pointer line down one side
Excellent - clean and ready to re-use
No need to have a flat sided shaft, these grip all around the shaft so they are often used with round shafts.
No grub screws or "push on"
How to access the securing mechanism
Flip off the top cap, unscrew the central bolt (slot head) and the knob releases from the shaft
Installation is the reverse procedure
All metal grip mechanism (brass)