Finding the right knob.
METAL with screw on side.2 kinds : 6mm and sometimes 6.35mm (1/4") for solid shafts (essentially Telecaster, Precision Bass)
PLASTIC push in. Always 6mm diameter hole. 2 kinds Metric with 18 splines. US 24 splines.
CTS = US. ALPHA or nothing on the pot = METRIC.
Exceptions : Chicken and Jazz Bass knobs. May have a 6 or 6.35mm hole. And have a screw on side or push in.
You can sometimes find asian metal knobs with plastic inside (6mm with 18 splines)