Originally Posted by
zukahn1
Also quill adapters have two sizes on each the size of the quill that goes in the fork and the size of the post top where the stem attaches.
Correct. Most have a true 1-1/8" outside diameter upper section where the stem goes and either a 25.4 mm diameter (1-1/8" steerer) or 22.2 mm (1" steerer) for the quill portion.