Barrel Diameter Vs. Pin Diameter

Barrel Diameter and Pin Diameter for a hinge are two dimensions that are sometimes mistaken for each other.  The Pin Diameter is just the dimension for the Pin which is the rod running through the curled leaves.  See dimension B on the picture.   The Barrel Diameter is the dimension across the entire pin and curled leaf, or the outside measurement. See dimension A on the picture.  Most hinge people will call out the pin diameter when referencing a hinge. See more information on hinge terminology here on the Guden Hinge Anatomy Glossary.