What size Allen Key - door mirror collar

[tvrbob]

I need to cut an Allen Key to fit into the door mirror recess so that I can tighten the collar grub screw. The dilemma is that I can't find out the size without first cutting the Allen Key. Just to save me some time effort and Allen Keys, does anyone know the Allen Key size for this grub screw?

[chevtrev]

Hi Bob
Its 3mm

[tvrbob]

Many thanks

[Andy JB]

I need to do this job - what do you mean by 'cut the allen key' ? is this a new technique to achieve this ?

[tvrbob]

A full size allen key is to long to fit between the grub screw and the recess in the door.