The available sling swivel are clearly illustrated by the following samples. Better grade swivels are available in both the US (25mm) belt width and Euro (20mm) Belt width.
Standard Fixed sling swivels
Detachable sling swivel
High grade Fixed sling swivels
High grade Detachable sling swivels
Full Stock Swivel
Concave profile Barrel Banded sling swivels. Available in Fixed or Detachable versions
Flat profile Barrel Banded sling swivels. Available in Fixed or Detachable versions