Here's a picture of the whole thing.
You can make one!
Here's a picture of the whole thing.
and here's a closeup of the business end.
Peter Paulovits in Germany reminded me that most of the world is metric,
and supplied the appropriate numbers:
Metric English A = 33 mm 1.3 inches or 1-5/16 " B = 43 mm 1.7 inches or 1-11/16 " C = 53 mm 2.1 inches or 1-2/32 "
And here's how to use it.