Same size as Pearl OptiMount hardware.
Quality control is a bit haphazard, so the first unit I received was scratched, dented and starting to rust in a few places, though nothing that compromised its function.
The junction point between the two halves doesn't have many dents, so it doesn't allow for many positions, which might make mounting the tom exactly how you like it a bit of a challenge, though after tightening the wingnut nothing moves even slightly, so if you don't mind the lack of QC and positioning flexibility it's the arm for you.
Also, despite not being in the pictures, the ones I received have plastic tops/caps at the ends of the tubes.