Alphason HR-100S Arm

Hi, It's an allen wrench inserted in the small hole on the platter side of the platform. The hole is offset to the rear and the wrench goes in at an angle. Don't know the exact size. They go from small, extra small, tiny, miniscule, and microscopic.  Tiny might get it.

I don't have a sizing block for these or I'd tell you. I pick them out by sight. If you want the exact size contact Audio Origami:

http://www.audioorigami.co.uk/tone-arm-rewires/

If you have the arm in front of you, you'll see the hole is not perpendicular to the cue lever cylinder along the mounting platform.  Because it's set back, it's a PIA to adjust. With the arm mounted on a table,.it might be impossible.  

Also, the headshell lifter is ridiculous, but this is easily replaced with a ProJect (or any) replacement part. You might have to snip off half the piece due to the central headshell protrusion.  Other than those minor faults, the arm has a lot going for it, most notably the one piece titanium construction. Eff mass is in the 11g range, but it performs more like a low mass arm with med/high cu cartridges, that is in terms of resultant transient response.. High mass arms tend to sound sluggish with those carts, IMO.