The shaft is 12mm (approximately 1/2 inch) long, 6.35mm (1/4 inch) diameter. The shaft comes with a M2.5-0.45 x 14mm screw.

Fits All My Poly (plastic) Variable Capacitors.

The 20.3mm knob fit these shafts. The shaft is not long enough for the 34.8mm knob.

20.3mm Knob