They are machined long and deep for better grip on smaller parts. The outside surface of the jaws is serrated to grip the work piece.
These jaws are called the #1 Jaws for the Stronghold Chuck, but can also be referred to as spigot jaws.
The serrations on the larger spigot jaws are on both the inside and outside of the jaws, whereas the serrations are only on the outside for the Talon spigot jaws.
The profiles are also quite different between the Talon and Stronghold spigot jaws. The Stronghold spigot jaws are taller and narrower with tapered portion at the top.
These jaws are not to be used with the woodworm screw.