Is this attachment what you guys are talking about? It's been attached to my dremel for so long now I forgot the name of it
I don't use the nibbler on my dremel anymore I much prefer the feel of the makita and terrier, feel like there's much more control. And power. Only use dremel for smaller jobs, the roto saws are great with a dremel and can give great hollowing out results with lots of control.
The hollow on the hornbeam is mostly rotosaw, rotary wirebrush and dremel
I also feel like this attachment gives you great control with it's ergonomic design