Sometimes the Fellows Stub and
American Standard Stub can be interchanged
by not with a full depth tooth.
Both the 4/5 and 8/10 Fellows Stub are
interchangeable with the 4 and 8 dp
stub gears.
In Europe, a truncated addendum design
can mesh with a full depth as they use
the same dedendums for both designs
as they use the same cutters to cut both.