Shocktech drop and 32degrees on/off question

[nouseforaname]

I just bought these for my mag and I cant get the on off to stay stationary because I cant get an allen wrench to fit in the hole on top ... does anyone know the size of the wrench that I need?

[spyxtra]

jsut try all the small ones you have in both metric and standerd 'cause it will make a dif