This knob is the standard cream Bakelite "S" switch and cable knob with Lucas pattern hexagonal mounting as fitted Lucas switches and Lucas classic car cables.

Fits on to the standard Lucas 1/4" hexagonal shaft with spring loaded retaining plunger.

Knob diameter  17/32" (13.7mm), Knob depth 1 & 1/4" (31.5mm). 

Note this is a high quality British made reproduction part.

Note price is per single knob with a number or knobs available, inset picture shows side and rear view with 1/4" hexagonal mounting hole and top view showing plunger hole. 

As fitted to a large range of Classic cars like; Morris, Mini, Austin, Jaguar, Hillman, Triumph, Allard, Armstrong Siddeley, Bristol, Daimler Jensen, MGA, MG Midget, Morris Oxford & Cowley, Rover, Singer, Triumph, Standard, Sprite, Vauxhall, Wolseley etc.