Joystick Shaft Diameter
Joystick Shaft size: the diameter shaft handle depends on wheelchair manufacturer.
Invacare chairs have .1875 inch (4.8mm) while most others are .25 inch (6.4mm). When measuring the shaft size of your wheelchair controller, be sure to remove the rubber cap or plastic knob that comes from the manufacturer. You will be measuring the metal shaft underneath.
For a quick check, .25 inch is about the diameter of a #2 pencil.