VPI 3-D tonearm

I think it's more of a medium mass

They do not list the mass of that tonearm on the specifications. I have never seen that omitted on any arm I have owned. I wonder why? It is an important spec to mate it with the cartridge you want to use.

Yogiboy:
I agree.
I want to add a stone cart from Koetsu but don't know if it'll be a good match.

Harry has said that he's installed almost every cartridge into the 3D with success. If it were I, I would call VPI with your question, but having many arms, none is as much as a "no arm" than is the 3D

I have use a Koetsu Azule on a 12-inch 3D arm. It sounds amazing. Prior to that, I had to use Damping fluid in a 12-inch metal VPI arm to get it to sound right.