Termite is a ring tool excellent for endgrain hollowing with large openings boxes, vases, goblets, etc
The cutting edge can cut from the bottom center to the rim or from a pilot hole to the side wall
It can pick up the cut in the center so a pilot hole is not required.
Another big advantage is that both sides of the ring cut so when one side gets dull just flip it over to the sharp side. Working wet wood it can clog once in a while - just flip it over and cutting from the other side spits out the clog.
There is a learning curve as Vern said
The hook tool is an alternative as are Other tools like a spindle gouge, a #4 or #5 Hunter, or the Monroe hollower and others.
I sharpen mine with with the Stone it came with mounted in a die grinder from habor freight.
Put the stone in the ring, hit the paddle on the die grinder and release, when the noise stops it is sharp on that side. Repeat on the other side.