This knob is for a LONG shaft potentiometer. From the bottom to the center of the set screws is ~11.5mm. You'll want your pot's shaft to stick up at least 13mm above the panel for these to mount correctly.(Note: Currently I do not carry pots with shafts this long.)
For a 1/4" smooth shaft.
It's numbered from 0-5.
Dimensions as measured with my calipers: HxW=20.6x23.5mm (29.1mm at the skirt)
About these awesome knobs: These are genuine Kilo International knobs. They are leftovers from custom runs for their clients. They are all in limited quantities and will most likely never be stocked in this style again. I have priced them all at half price of their Digikey equivalent.
If you're interested in them, I would grab as many as you can now. They won't last.