This is a speed handle for the Panavise Jr, modeled against the knob geometry of the 201. I believe it should be compatible with Panavise models 201, 203, 207 and 209 as well.
The grip has threads modeled into the end to accept the nut, but in my experience, I did have to chase the threads as a post-process because of the print orientation and minor inconsistencies.
I've included a set of files that use an M5-08 thread and nut, and a set of files that use a 1/4-20 thread and nut, with a clearance hole in the drive appropriate for each. If you don't have a tap and die set, you can usually use a spare screw and nut to clean up the threads if you print this in PLA.
The threads on the grip are modeled so they end 0.5mm below the bottom face of the drive arm, which should allow you to tighten (relatively, it's plastic after all) the nut down and still have free rotation. If it's too loose for you, just extend the threads up a bit using either a die or a real nut, to snug things up. It should spin freely but not be overly sloppy.
I used a couple drops of superglue as loctite to permanently secure the nut on the end of the grip.