What size Allen key?

[Holleyman]

I have used a T6 Torx bit to undo the allen set screw that holds the castle nut on the m305 flash suppressor because I don't won the correct size allen key. I went to the local Mac dealer today looking for the correct allen key size and he also didn't have one! I tried metric but 1.5 mm is too small and 2.0 is too big, I tried standard but 5/32 is too big and 1/8 is too small.
What weird size has China come up with for this damn set screw, I checked all of the stickys that Skullboy has and he states "small set screw", no size.

Help!

 

[mdbuckle]

I had to file one down to get it to fit...it is a weird size.

 

[Tehoke01]

A 1.75 allen key would probably be perfect but since they apparently don't exist...

...just go with a Torx, as "they" say, if it works, use it.