New Moto Guzzi Door Mats Available Now
About as often as the 5.5mm and 7mm allen keys that are in every set...
Ducati bevel cylinder head nuts.http://www.ebay.com/itm/Ducati-Torque-Wrench-Tool-Cylinder-Head-750-860-900-1000-SS-Darmah-GT-bevel-16MM-/181980086969?hash=item2a5edbc2b9:g:AHsAAOSwofxUdOO6
Peugeot 505 starter motor had 16mm and someone had stuck an old Witworth clamp on the exhaust!!I know I've used the 18mm - can't remember where.Maurie.
Several GM products use both sizes. The 18mm more than the 16. One place that I remember was in the brake caliper area.