What size are the allen bolts that hold the front calaper is not 8 or 10mm on 2006 Mercedes-Benz R350

Does it take a special tool,

Asked by for the 2006 Mercedes-Benz R350
The workshop manual does not have a good illustration of the bolts or identify what size it is, look carefully at the head of the bolt to see if it has a Hex head or Torx head or some other spline type head. Your question may be best posted on a Mercedes SUV forum.