Buy a MM Allen set and then you can't go wrong.
To fasten and unfasten Allen screws and bolts. These fasteners have a hexagonal slot in the top into which the Allen wrench or key fits.
a hexagon
Hexagon
6-sided is hexagon
To determine the size of the rounded Allen wrench needed for the task, measure the diameter of the screw head or the hole it fits into. Match this measurement to the corresponding Allen wrench size.
hexagon
I believe that's a 5/16 Allen.
Hexagon
whatever one fits, some are torx..
Allen keys are hexagonal. The shape is a hexagon (6 sided figure).
this is my question, lol. my answer is 7 mm Allen wrench. fits like a glove!
I believe that would be a 3/8 Allen wrench. -Very common on Dodge /Plym brakes.