Mercury style aluminum knob. Comes with a 1/8″ pilot hole that you can enlarge if necessary for your application comes with a side set screw which is already installed.
Also comes supplied with this neat collar to finish off that switch which can be screwed on if you have the same thread or attach by whatever means.
DSS Ford & Mercury style dash knobs fit up to 3/16″ diameter shafts, perfect for any of our dash switches with shafts these can also be drilled to fit much larger shafts.
Fastens with 8-32 set screw, collar has a 7/16″ (12mm ish) hole.