A bit confusing using two letters to indicate measurement units in some cases and two letters to indicate model in others. But I guess until they make a model that uses 'FR' as an abbreviation for its name we'll be OK....

White's used metric units in some of their coil names to indicate size. In many cases it's pretty easy to figure out whether the units are inches or centimeters. A 33 inch coil? Probably not. A 6 cm coil? Probably not.