The standard pot type,
Cheap & robust, the Alpha 16mm is the default type in audio/instrument projects where control pots can be a major part of the total cost. A chore is in having to cut the 20mm shaft down. A star docked for that. Very few knobs have as much as 12mm shaft clearance and a little more is needed to cover the nut. A 10mm shaft length would be better for me.