Most motor axles (Crystalyte 400 series, Wilderness motors) have 12mm axles.  Motors with 12mm axles are able to use a standard freehwheel removal tool, although motors such as BMC, Puma or Crystalyte 500 series require a freewheel removal tool big enough to fit over these large axles.  The Custom Freewheel removal tool has been machined to fit over all larger motor axles.